[Cooling System]
[From the U.S. Government Publishing Office, www.gpo.gov]

COOLING SYSTEM:
CLEANING, FLUSHING, RUST PREVENTION, AND ANTIFREEZE
Prepared for vehicle maintenance section
DIVISION OF MOTOR TRANSPORT
OFFICE OF DEFENSE TRANSPORTATION
by MAINTENANCE METHODS COORDINATING COMMITTEE OF TRANSPORTATION AND MAINTENANCE ACTIVITY SOCIETY OF AUTOMOTIVE ENGINEERS, INC.
GOVERNMENT PRINTING OFFICE - WASHINGTON - 1943
SAE Maintenance Methods Coordinating Committee
W. J. Cumming, Chairman, Chief, Vehicle Maintenance Section Division of Motor Transport Office of Defense Transportation
E. P. Gohn, Test Engineer The Atlantic Refining Company
M. E. Nuttila, Superintendent, Motor Vehicles Cities Service Oil Co.
G. W. Laurie, Manager, Automotive Transportation Department The Atlantic Refining Company
J. Y. Ray, Supervisor, Automotive Equipment Virginia Electric & Power Company
S. B. Shaw, Automotive Engineer Pacific Gas & Electric Company W. A. Taussig, Automotive Engineer Burlington Transportation Company E. W. Templin, Automotive Engineer Los Angeles Department of Water and Power D. K. Wilson, Superintendent, Automotive Equipment
New York Power & Light Corporation
A. M. Wolf, Automotive Consultant
(H)
Subcommittee on Cooling System: Cleaning, Flushing, Rust Prevention, and Antifreeze
D.	H. Green, Chairman, Service Manager National Carbon Company, Incorporated F. R. Archibald, Technical Supervisor National Carbon Company, Incorporated J. Askin, Chief Engineer, Radio Division Fedders Manufacturing Company, Incorporated J. D. Bradley, Fleet Superintendent
American Ice Company E. Chadwick, Fleet Manager Little Falls Laundry Company H. C. Duus, Chemist E. I. du Pont de Nemours & Company L. R. Gwyn, Jr., Engineer, Automotive Department Railway Express Agency, Incorporated
E.	N. Hatch, Service Engineer American Brakeblok Division
W. R. Herfurth, Superintendent, Automotive Equipment
R. H. Macy & Company, Incorporated
J. J. McCarron, Superintendent, Garage Consolidated Telegraph & Electrical Subway Company C. E. Smith, Shop.Superintendent Burlington Transportation Company
H. M. Smith, Superintendent of Equipment Connecticut Railway & Light Company G. E. Stewart, Parts Manager United Parcel Service of New York, Incorporated W. A. Taussig, Project Chairman
(in)
TABLE OF CONTENTS
IMPORTANCE OF PREVENTIVE COOLING-SYSTEM MAINTENANCE 	_		Section A
INSPECTION AND TESTING FOR COOLING LIQUID LOSSES 		B
Inspection for cooling liquid losses_  	_	_	_		_	B-l
	
Liquid level in radiator _ 		 .. .. _ 	 _	_		 . _	_ _ _	B-2
Inspection for leakage	_	_______	_	_. .. 	 _____	B-3
	
Pressure testing for cooling system leakage	___	_		 _	B-4
	
Internal leakage of the engine water jacket	__		 _	B-5
Service tests for internal engine leakage	_	_	_ _			 _ _	B-6
Inspection for water-pump leakage	_	_			B-7
	
Service test for air suction into system	____	....	 __	B-8
Overflow loss from air or gas entrainment in liquid	........			B-9
Method for observing air or gas in cooling liquid	__	_ 				B-10
	
Overflow loss from local boiling in water jacket				 		B-U
Service test for overflow loss of cooling liquid				 _ _ 	 . _	B-12
Maintaining a “standard” liquid level in radiator		 _		 __	B-13
	
ROUTINE MAINTENANCE OF COOLING SYSTEM	 . 		C
Radiator and hot-water heater	_ _	__			 __ 		C-l
Radiator top tank baffle __				 ____			 ___ 		C-2
Radiator cap	_ _	_. _ 		C-3
Pressure caps in sealed cooling systems	_			 .......	_ _	C-4
Radiator overflow tank	. ..		 		C-5
Rubber hose connections	_ 		C-6
Engine water-jacket joints and gaskets	C-7
	
Cylinder-head-gasket joints				C-8
	
Water pump and fan	 	 	 	 .	C-9
Thermostats.	.	-	C-10
Radiator covers and manually operated shutters			C-ll
	
Thermostat, testing	_	_		 _	_ _	C-12
Effect of altitude on thermostat operation	_	_ 		C-13
Water-distribution tubes-__	_		 _	_	_ -	C-14
DIAGNOSIS OF OVERHEATING AND OVERCOOLING_ 		 _	. . .   _	D
Overheating of engine				 					D-f
Overcooling of engine						—			D-2
COOLING-SYSTEM CORROSION AND ITS PREVENTION		E
Aeration of the cooling liquid		 .. .	.	E-l
	
Mineral salts in natural water supplies______^				E-2
Incidental contaminants	*	- -.— - -		E-3
Effect of temperature on corrosion	„		—	E—4
Typical corrosion damage of cooling system parts		E-5
Treatment of water for corrosion prevention			E-6
COOLING-SYSTEM CLOGGING AND METHODS FOR PREVENTION		F
Water-scale formation			F-l
Prevention of water scale				F-2
Preventive cleaning of cooling system (chemical)			4		,		F-3
Preventive cleaning procedure					F—4
Preventive flushing procedure			F-5
Corrective cleaning of the cooling system				F-6
“Pressure” flushing procedure	:		F-7
Special corrective cleaning methods	-			>—	F-8
(IV)
CONTENTS	V
CHARACTERISTICS OF DIFFERENT TYPES OF ANTIFREEZE	 Recommended antifreeze materials	_ _ -				Section 	 G G-l
Nonrecommended antifreeze materials	_			G-2
Freezing protection	_				G-3
Boiling point characteristics		......	G-4
Effect of altitude and pressure on boiling point		 Foaming tendencies of cooling liquids	_	. . 	 ..	,		 G-5 G-6
Creepage of antifreeze solutions	_ 			 ..				G-7
Thermal expansion of antifreeze solutions	......	G-8
Chemical characteristics of organic antifreeze solutions					 Installation, testing, and servicing of antifreeze	_			G-9 G-10
Conservation of used antifreeze solutions 		    ....			 G-U
Figure 1.—The automotive cooling system, showing points in the cooling system where trouble may result from neglect of cooling system service.
Cooling System: Cleaning, Flushing, Rust Prevention, Antifreeze
A.	IMPORTANCE OF PREVENTIVE COOLING SYSTEM MAINTENANCE
Every commercial vehicle operator should carefully restudy his cooling-system maintenance methods, particularly in the light of present war emergency conditions of discontinuance of motorvehicle production for civilian use, shortage of replacement parts and labor, and increasing demand on existing vehicles for essential services connected with the war effort.
Preventive cooling-system maintenance service, in the real sense of the word, should be practiced. For example, overheating of the engine from loss of cooling liquid should be avoided by preventive inspection and servicing for leakage and overflow losses rather than by continually adding water or valuable antifreeze. Likewise, the problem of rustclogging and corrosion damage should be eliminated by the prevention of corrosion rather than by the correction of rust-clogging through clean-out methods or the replacement of damaged parts containing critical materials after the cooling system is in trouble. (See flg. 1.)
Generally speaking, preventive cooling-system maintenance never has been up to the standard of service for other units of the vehicle. It is therefore all the more important that a higher standard should be set and constantly maintained during these critical times to prevent conditions of neglect that otherwise will result in gasoline wastage, lubricating difficulties, and excessive wear or damage of the engine from either overheating or overcooling.
The importance of maintaining the automotive cooling system as close as possible to new-car efficiency at all times can be appreciated if it is realized that even in the smaller engines the amount of heat which must be dissipated through the cooling liquid and radiator is sufficient to heat a 6-room house on a zero day. The amount of water pumped at high speed in such an engine would fill a 50-gallon drum in 60 seconds. Complete' failure of cooling for any reason means dangerous overheating of the engine in a few minutes. Proper cooling contributes more to continued engine operation and long life than is
generally realized. Many expensive road failures are caused by the simplest irregularities that very often could have been detected and corrected through a few minutes’ close inspection before the vehicle left the shop.
B.	PREVENTIVE INSPECTION AND TEST-
ING FOR COOLING LIQUID LOSSES
The suggested tests which follow have all been used in actual maintenance, but are not intended to be mandatory. The condition of each individual vehicle should determine if any or all tests are needed. Which tests are necessary, desirable, or possible must be left to the judgment of the vehicle operator.
B-l. INSPECTION FOR COOLING LIQUID LOSSES
Considering the engine damage which can result from overheating when a vehicle is driven with insufficient liquid in the cooling system, the maintenance of proper liquid level in the radiator is of first importance. Contrary to the popular belief, evaporation of water or antifreeze solutions accounts for only a small part of cooling liquid losses. Large-scale driving tests have proved that, on the average, at least half of all the cooling liquid loss from a system is due to leaky parts, and that most of the other half is liquid loss through the radiator overflow pipe from boiling, foaming, etc. Only by careful preventive inspection can motor-vehicle operators avoid the trouble and expense of replacing cooling-liquid losses and the hazards of overheating damage from shortage of cooling liquid. (See fig. 2.)
The level of cooling liquid in the radiator is the focal point of preventive cooling-system maintenance, and is just as important as the oil level in the crankcase.
B-2. LIQUID LEVEL IN RADIATOR
The first check on coolant losses is the inspection of the liquid level in the radiator. This should be performed daily. Wherever possible it should be done when the liquid is heated up' to driving tem-
(1)
2
perature and after the engine is stopped. A convenient time to check the level in the radiator is when the vehicle is put up at the end of the day or working shift. The reason for stopping the engine before checking the liquid level is to permit the escape of any air or gas that might have become entrained or mixed with the liquid during operation.
Figure 2.—Cracked engine block typical of damage from overheating.
Air or gas entrained with the liquid gives a false high level in the radiator which drops when'the engine stops and circulation of the liquid ceases.
Caution: Do not use a match or other open flame when inspecting the liquid level in the radiator.
Both water and antifreeze solutions take up more room in the cooling system when hot than when cold.
Figure 3.—Above: Showing overfilling of radiator when solution is cold; Below: Showing how solution is lost through overflow pipe by heat expansion when too much water is added with solution cold.
If the radiator is filled too full when cold, expansion when hot will overfill the radiator and liquid will be lost through the overflow pipe. Adding unnecessary water weakens antifreeze solutions and eventually leads to a freeze-up. In many vehicles it is impossible to see deeply into the radiator due to the design and location of baffle plates or elbow filler necks, and if a service man checks the solution when it is
cold, he may not be able to see it and may think it is low when it really is not.
It is advisable to avoid making any additions of cooling liquid as long as the hot level is well above the top of the radiator tubes or is in sight through the radiator filler opening. Because of the many different designs of cooling systems, it is not possible to set a universal standard for liquid level that will apply to all makes of vehicles. However, in any vehicle, the hot liquid level should be sufficiently far below the top of the overflow pipe, with the engine stopped, to insure that no liquid will overflow under conditions of driving. Vehicle manufacturers’ directions should be followed for proper height of liquid level. (See fig. 3.)
B-3. INSPECTION FOR LEAKAGE
It is not safe to assume that daily losses of cooling liquid are evaporation losses. Even when the amounts are small, they warrant an immediate investigation of the cause, and the possibility of leakage should never be overlooked. Leakage of only 1 drop of liquid per minute means 1 gallon of antifreeze solution lost in 6 weeks. Leakage of the cooling system is probably more prevalent than of any other liquid-carrying unit in the vehicle, due to the stresses and strains set up in joints and connections by wide changes in engine temperature, especially during cold weather; vibrations from operation of the engine and movement of the vehicle; deterioration of gaskets; and wear, breakage, or corrosion perforation of metal parts. Leakage is thought to be the most common trouble in the cooling system itself.
To detect small leaks at their inception, inspection should be made with the cooling system cold, preferably before the vehicle is put into operation for the day. Small leaks which may show dampness or even dripping when cold can easily escape detection when the engine is hot, due to rapid evaporation of the leakage. This is particularly true of water and alcohol and antifreeze solutions. High-boiling-point antifreezes of the ethylene-glycol type evaporate more slowly, and any existing leakage of their solutions is therefore easier to find. Telltale stains of grayish-white or rusty color, or dye stains from antifreeze, at joints in the radiator or engine water jacket are almost always sure signs of small leaks even though there appears to be no dampness. These stains are usually corrosion products from the cooling system, which have been carried through the leaking crevices and left behind when the cooling liquid has evaporated.
Certain parts of the cooling system are difficult to inspect for leakage, such as the rear of the engine water jacket, some drain-plug locations, the front side of the radiator in the newer cars with grilles, the underside of the radiator bottom tank, and the
3
water-pump seal which in some cases is practically covered up by the driving pulley. Because of the inaccessibility of these points to leakage inspection, it is advisable to locate vehicles overnight on a clean floor surface, and then inspect the floor for wetness in the morning after the vehicle is moved from the parking spot.
Points of liquid leakage commonly occurring in the cooling system are: Radiator, cylinder-head-gasket joint and studs, waterpump shaft, hose connections, engine castings cracked or porous, water-
Figure 4.—Outside leakage of engine water jacket. *
jacket core-hold plugs and cover plate, thermostat and pump housings, drain cocks, water-jacketed oil lines and coolers, and hot-water car heater. (See fig 4.)
B—4. PRESSURE TESTING FOR COOLING SYSTEM LEAKAGE
Inspection for liquid leakage may not detect leaks above the liquid level in the radiator. The application of vacuum or pressure to the cooling system by mechanical means requires experience and care to avoid damage and special pressure control equipment is necessary. A simple test for airtightness can be made, with the cooling system cold, by sucking on a rubber tube attached to the overflow pipe and then applying the tongue to the end of the tube. If the tongue adheres to the tube, the system may be considered reasonably airtight. For personal safety reasons, getting cooling liquid or antifreeze solution in the mouth always should be avoided. In sealed systems, the radiator-cap pressure valve must be blocked open while making this test.
B-5. INTERNAL LEAKAGE OF THE ENGINE WATER JACKET
While outside leakage of the cooling system, if neglected, introduces the immediate hazard of overheating from low cooling liquid, inside leakage of
the water jacket into the crankcase and moving parts of the engine can be even more serious in its consequences. Common points of internal leakage are: Loose cylinder-head-gasket joints, thread leakage of loose cylinder-head studs or bolts, seal leakage on wet-type cylinder sleeves, porosity or cracks in the cylinder head or block, and loose or broken joints in oil coolers or oil lines in contact with the cooling liquid.
Either water or antifreeze solution leakage into the engine is detrimental to lubrication, and either liquid mixed with the engine oil in sufficient quantities will form sludge which may cause lubrication failure, sticky piston rings and valves, excessive wear, and extensive engine damage if driving is continued. Appreciable quantities of water and antifreeze may be removed by crankcase ventilation and do no harm, in warm weather but may cause serious engine trouble during cold-weather driving. For this reason, a preventive check for internal leakage should preferably be made in the fall of the year, as a regular part of a winter maintenance program. (See fig. 5.)
Figure 5.—Liquid leakage into engine.
B-6. SERVICE TESTS FOR INTERNAL ENGINE LEAKAGE
Checking for internal leakage of the engine water jacket is not as simple as inspection for outward leakage of the system. However, there are several tests which, if performed regularly, will detect most internal leakage before it reaches the serious stage. These tests are made as follows:
1.	Start with the engine cold, first removing the fan belt from the drive pulley, or disconnecting the water-pump coupling, to prevent pump operation. Drain the system until the coolant is level with the top of the engine block, but no lower. Remove the upper radiator hose, thermostat housing, and thermostat. Replace the thermostat housing and
540656°—43---2
4
fill with water; or, with the housing removed, fill the water jacket completely.
With the engine in neutral gear, “gun” it several times, watching for bubbles m the water opening while gunning, and also when the engine drops back to idling. To detect the smaller type of leaks, jack up the rear wheels of the car, run the engine at higher speed in high gear, and load it gradually and intermittently by the use of the foot brake.
Appearance of bubbles or the sudden rise of liquid indicates leakage of exhaust gas into the cooling system. Injectmg suitable light oil into the carburetor while testing sometimes helps to identify exhaust gas leakage by producing smoke in the bursting bubbles. Make the test quickly before boiling starts since steam bubbles give misleading results. Even a small amount of exhaust gas leakage into the cooling system should be corrected immediately, since the indicated gas leak may eventually permit liquid to enter the engine if it is not already doing so. (See fig. 6.)
2.	Using an adaptor, apply air pressure (about 100 pounds) through each spark-plug hole with the piston at top dead center on the compression stroke. Air-leakage from the cylinder will be indicated by air bubbles or a rise of liquid in the radiator or in the engine water outlet if the upper hose is disconnected. This is also a useful test for valve leakage.
Figure 6.—Cheeking for exhaust gas leakage.
3.	The “smell” test, made at the radiator filler opening, is reported to be of value, since exhaust gas leakage into the cooling system seems to give the cooling liquid a distinctive odor.
B-7. INSPECTION FOR WATER-PUMP LEAKAGE
It should be pointed out that a pump-seal leak which is dripping with the engine stopped or idling may not show up at all with the engine running at moderately high speed, for the reason that the suction of the running pump will draw air in at the leak and thus prevent liquid from running out. This
Figure 7.—Points of leakage in two types of water pumps: Left, in “packless” type pump seal; right, in adjustable gland-type pump seal.
same condition exists at all points of leakage on the suction side of the water pump, including heater hose connections to the engine and. car heater, lower hose connections between pump and radiator, lower tank of the radiator, and even at leaks in the lower portions of the radiator core. (See fig. 7.)
B 8. SERVICE TEST FOR AIR SUCTION INTO SYSTEM
Since water-pump leakage cannot always be detected by casual inspection, a special test may be necessary. The following quick check for leaks on the suction side of the water pump usually requires no other equipment than a piece of tubing and a glass bottle containing water.
To make this test, first adjust the liquid level in the radiator, allowing room for expansion when hot, so as to avoid any overflow loss during the test. Be sure the radiator cap is on tight. With pressure caps, block open the pressure valve or replace with a plain cap.
Attach a suitable length of rubber hose to the lower end of the overflow pipe. All connections must be airtight. Run the engine in neutral gear at a safe high speed until the dash indicator stops rising and remains stationary; in other words, until the engine
Figure 8.—Checking for air suction.
5
reaches a constant operating temperature. Without changing the engine speed, put the free end of the rubber tube into a bottle of water, avoiding kinks and low bends that might block the flow of air. Watch for bubbles in the water bottle.
In the absence of exhaust gas leakage into the cooling system, a continuous flow of bubbles indicates that air is being sucked into the system.. Any leak on the low-pressure side of the pump, which wul permit air to be drawn in at high speed, will eventually allow liquid leakage with the engine idling or stopped, if liquid leakage is not already present. (See fig. 8.)
B-9. OVERFLOW LOSS FROM AIR OR GAS ENTRAINMENT IN COOLING LIQUID
As previously stated, during operation of the engine at higher speeds, suction of the water pump will draw air into the system through leaks at the pump seal or at other points of leakage on the low-pressure side of the pump. This air is circulated with the cooling liquid and increases the volume, of the liquid in the system, causing.the level to rise in the radiator. Entrained air, in sufficient quantities, causes large overflow losses of cooling liquid while the vehicle is being driven.
In the case of an internal water-jacket leak, exhaust gas may be blown into the cooling system under the explosion pressures, even though the leaks may be too small to allow liquid leakage into the engine. Exhaust gas entering the cooling system will act in the same manner as air suction into the system from the pump. The volume of the liquid in the system is increased, and the level in the radiator may rise to the overflow point.
With reduced engine speed, air suction ceases, and at low engine speed and output, exhaust gas leakage may diminish. The air or gas already entrained in the liquid escapes to the air space in the upper radiator tank, causing the level in the radiator to drop. Therefore, an inspection of the liquid level with the engine idling or stopped will not reveal the abnormally high level prevailing with the vehicle running.
B-10. METHOD FOR OBSERVING AIR OR GAS IN COOLING LIQUID
Air or gas entrainment in the cooling liquid may be readily observed through a glass tube installed in the upper hose. A section of the hose is cut away and the glass tube is inserted and secured to the hose ends with suitable clamps. With the engine running at the higher speeds, any air or gas in the cooling liquid appears as bubbles passing upward in the tube. Finely divided bubbles, indicating foaming, will impart a milky appearance to the liquid. To avoid confusing exhaust gas or air bubbles with steam, the temperature of the cooling liquid should be kept well below its boiling point during the test. (See fig. 9.)
Figure 9.—Detection, of gas entrainment with glass tube: Left, aerated coolant; right, air-free coolant.
B-ll. OVERFLOW LOSS FROM LOCAL BOILING IN WATER IACKET
Fleet operators seem to be in agreement that overflow losses from hot spots and local boiling in the engine water jacket are quite general conditions. When the engine is slowed down or stopped after driving, steam pressure in the water jacket forces cooling liquid into the radiator until it overflows. This phenomenon is commonly known as afterboil. Common causes of hot spots are rust and scale
Figure 10.—Overflow loss from overheating and boiling.
clogging the water passages in the jacket, especially between cylinders and around the exhaust valves. (See fig. 10.)
B-12. SERVICE TEST FOR OVERFLOW LOSS OF COOLING LIQUID
The detection of overflow loss of cooling liquid must be made while the vehicle is being driven or immediately after it is stopped. For accurate checking oi overflow losses, a catch pot in the form of a gallon can or glass jug on the radiator overflow pipe is indispensable. The catch pot is located at a point below the normal solution level in the radia
0
tor and is connected to the radiator by a tube attached to the overflow pipe. Kinks and low bends in the overflow tube must be avoided, and the end of the tube must not extend into the catch pot more than an inch, while the catch pot must be open to the atmosphere. A convenient installation is a 1-gallon glass jug located on the floor of the vehicle below the instrument panel and visible from the driver’s seat.
Before making a test run with the vehicle, the solution level must be adjusted with the engine at driving temperature so as to eliminate the possibility of overflow loss from overfilling and thermal expansion during the test. During the test run, the vehicle should be driven under customary conditions of speed and load for sufficient distance (not less than 5 miles) to obtain maximum engine operating temperature, following which the vehicle should be decelerated and stopped and the engine shut off, in accordance with regular driving practice. After repeating this procedure a few times, any overflow of cooling liquid which has collected in the catch pot should be measured to determine the amount of loss from the system through overflow for a given driving period.
Driving overflow losses should always be kept down to the absolute minimum. Certainly a vehicle which requires additions of liquid during a normal driving shift should be put in the shop for detection and correction of the cause. One operator of large buses makes a practice of putting vehicles into the shop for inspection and servicing if the cooling system requires more than 2 quarts to be added per day.'
B-13. SUGGESTIONS FOR MAINTAINING A
STANDARD LIQUID LEVEL IN RADIATOR
1.	In larger fleets where it may not always be practicable to check the liquid level at top engine driving temperature, a standard level at a lower temperature may be established. For the purpose of maintaining a standard liquid level at any established temperature, a simple home-made gauge can be prepared in the form of a T. With the horizontal member of the T resting on the top of the filler neck opening, the vertical member is of such length as to just touch the liquid at the standard level. (See fig. 11).
Figure 12.—Sight gauge, showing radiator liquid level.
7
Figure 13.—Testing antifreeze through sight gauge opening.
2.	Due to long, curved, or offset fillers in rear-engined buses and cab-over-engine trucks, visual inspection of solution level is often impossible. In such cases, a satisfactory method of checking the level has been obtained by installing a petcock on the side of the top radiator tank at a previously determined standard liquid level and temperature. With the petcock open, the liquid level is adjusted to the point where liquid starts to run out the petcock, after which, of course, the petcock is closed.
3.	An inexpensive water-sight gauge installation on a cab-over-engine vehicle is illustrated in figures 12 and 13. Reports on this installation indicate that it has been effective in reducing water additions . to the system. This type of installation has the advantage of accessibility for inspection of cooling liquid condition, for filling, and for antifreeze testing.
Even when using water only, during warm weather or in vehicles regularly parked in heated garages, overfilling should always be avoided. Nearly all water supplies contain some dissolved minerals
which have a tendency to precipitate and form scale deposits in the system, especially at any hot spots in the engine water jacket. Another reason for adding to the system as little water as is consistent with proper circulation and cooling is to avoid the loss of corrosion protection from thermal expansion and overflow, when using a corrosion inhibitor in the water.
C.	ROUTINE MAINTENANCE OF THE COOLING SYSTEM
Regular preventive inspection and maintenance service are the only sure means of keeping the cooling system leak-tight, clean, and in proper working order, and of maintaining new-car cooling efficiency at all times. Prompt detection and correction of minor irregularities by tightening, adjustments, minor repairs, rustproofing, and cleaning will prevent engine failure and expensive repairs or replacements of scarce parts.	—
8
C-l. RADIATOR AND HOT-WATER HEATER
Radiator-drainplug leakage should be corrected immediately by tightening or applying nonhardening compound to the threads. Drain cocks that do not close tightly may require replacement.
To prevent breakage of soldered seams and connections, strain and vibration should be avoided in the radiator as far as possible. Radiator anchor bolts should be checked frequently for tightness and any strains on the radiator or connections relieved by suitable adjustment. Where the cab dash is used as the anchor for upper radiator stay rods, the cab-to-frame hold-down bolts must be kept snug to prevent movement and strain of top of radiator. Engine vibration and vehicle movement should not
Figure 14.—Seam leakage of radiator core.
be overlooked as causes of joint failures in. the radiator core, tanks, and inlet and outlet fittings. Extreme changes between atmospheric and operating temperatures, especially in winter, set up additional strains that may cause seam breakage. When the seams break, the solder corrodes out; but breakage rather than corrosion is the most general cause of radiator leakage.
Neglect of small seam leaks may result in a complete radiator failure, as well as leakage, overflow loss, rust-clogging and overheating difficulties. For permanent repairs, soldering by an experienced radiator man is strongly recommended. Stop-leak preparations may seal small leaks, but cannot be depended on for permanent correction of the leakage. Even soldering is not generally practicable for repair of
leaks resulting from corrosion perforation of the thin water-tube walls in the core. A stop-leak preparation may seal corrosion leaks temporarily, but usually corroded qores must be replaced. (See fig. 14.)
At least monthly or at each lubrication period, the appearance of the cooling liquid, as regards color, rust, etc., should be checked with the engine at driving temperature and running. More frequent checks can be made without extra work by observing the solution condition in the hydrometer when testing antifreeze. A rusty solution indicates the immediate need of rust-prevention treatment. Heavy rust deposits in the radiator call for prompt cleaning of the cooling system. Cold spots on the radiator core, with the engine hot, indicate clogging.
With radiator-clogging, pump vacuum increases in the bottom tank of the radiator and in the connections to the inlet side of the water pump. To test clogging, limited use is known to have been made of a vacuum gauge connected to an open radiator drain cock for checking radiator water-tube restriction. A pressure-vacuum type of gauge should be employed, since pressure is developed on the inlet side of the pump under certain conditions. Vacuum testing for radiator-clogging would require a previous knowledge of normal vacuum, with the radiator clean, to be dependable.
Another way to test clogging is offered by observation of liquid level rise in radiator top tank. When flow through the radiator core is restricted, accelerating the engine with the vehicle standing will cause the liquid level to rise and possibly overflqw. Liquid level rise in some vehicles may be observed through the open filler neck.
The prevention of radiator corrosion damage, and also rust clogging, are discussed in detail in sections E and F.
C-2. RADIATOR TOP TANK BAFFLES
Sheet-metal baffle plates of various designs are installed in the upper tanks of radiators to more uniformly distribute the flow of liquid through the water tubes and to prevent pumping over and excessive turbulence of the liquid entering the tank, which would cause aeration, air entrainment, foam-ing, and overflow loss. Occasionally the baffles break loose and interfere with the proper flow of liquid. It is therefore important, when making periodic inspections of the radiator, that the condition of the baffles should be examined through the filler opening.
C-3. RADIATOR CAP
The radiator cap is subjected to high temperatures which cause relatively rapid deterioration of the gasket. Leakage of the radiator cap may result in cooling liquid being thrown on the engine, which, in
9
the case of alcohol antifreeze, creates a fire hazard, especially with overheating and boiling. Ignition of alcohol vapor under the hood may spread to the lower opening of overflow pipe when the vehicle and engine are stopped. With the vapor burning at the overflow pipe outlet, removal of the radiator cap may result in the flame traveling up through the overflow pipe and causing a burst of flame out of the filler opening.
The underside of the radiator cap is exposed to the extremely corrosive effects of a hot steam and air mixture in the air space of the upper tank during driving. Since the cap is above the normal liquid level, it receives little or no protection from any corrosion inhibitors in the liquid, with the result that bayonet-type radiator caps often fail from corrosion damage.
The radiator cap and joint should be inspected regularly and deteriorated or leaking gaskets and badly corroded caps promptly replaced.
C-4. RADIATOR PRESSURE-CONTROL CAPS IN SEALED COOLING SYSTEMS
Many vehicles of recent make have built into the radiator cap a normally closed valve which is designed to permit 3 to 9 pounds steam pressure in the system before opening. This pressure raises the boiling point of the cooling liquid and permits some-
Figube 15.—Radiator-pressure-control cap.
what higher engine-operating temperatures without overflow loss from boiling. If the steam pressure becomes great enough to open the valve, the pressure drops and sudden violent boiling may occur with large overflow losses. Steam pressure in a sealed cooling system increases the leakage tendency at hose connections and water joints. To prevent the collapse of hose and other parts which have, no internal support, a second valve in the radiator cap
of a conventional sealed cooling system opens under vacuum when the system cools.
If a cooling system with the pressure valve radiator cap is overheating, remove the cap slowly and carefully to avoid possible flash of steam and hot cooling liquid that would scald the face and hands as well as spot the vehicle finish. Pressure radiator caps should be inspected frequently for tightness of the gasket joints. To avoid possible damage to the system from either excessive pressure or vacuum, both valves in the cap should have a periodic check of proper opening and closing pressures, and should be serviced or replaced in accordance with the vehicle manufacturer’s directions. (See fig. 15.)
C-5. RADIATOR OVERFLOW TANK
Usually installed as an accessory, radiator overflow tanks are located under the hood of the vehicle. A lower opening in the tank is connected to the radiator overflow pipe, and an upper opening is vented to the atmosphere. The tank acts as an emergency container for overflow of cooling liquid from the radiator while driving or immediately after the engine is stopped. The overflow tank is designed to return to the cooling system by vacuum, when the engine cools down, any overflow occurring from boiling. Proper functioning of the overflow tank depends on maintaining an airtight cooling system, including tight connections and free, unobstructed flow between the radiator and the tank. If either liquid or air leaks develop in the cooling system and cause failure of the vacuum, any overflow into the tank will not return to the radiator, and liquid will be lost when the tank overfills. When, upon stopping the engine, overflow of cooling liquid from afterboil is large, it may overfill the tank and cause overflow onto the engine, introducing a fire hazard in the case of alcohol antifreeze. If the tank developed a leak, the same hazard would exist as from corrosion perforation occurring in a steel tank.
C-6. RUBBER HOSE CONNECTIONS
Hose clamps should be checked, and tightened if necessary, at least every 30 days or 1,000 miles, and clamps which buckle the hose or do not make tight joints should be replaced. Engine vibration has a tendency to loosen hose connections. Each time the hose connections are opened for any reason, carefully examine the inside lining. Inspect the inside of heater hose every fall and radiator hose every 10,000 miles and replace if necessary. When installing new hoses, clean the pipe connections and apply a thin layer of nonhardening sealing compound. Do not use grease of any kind on hose. Forcing undersize or swollen hose over the pipe connection may tear the inner liner and cause it to
10
protrude into the coolant stream and restrict circulation. Be sure hoses are installed without kinks or sharp bends. Reinforcing springs inside radiator hoses should be checked for corrosion. Do not fail to check the condition of underseat heater hoses.
The quality of hose has more to do with its service life than standard cooling liquids. Overage hose
Figure 16.—Inside deterioration of water hose.
failures are due to swelling, hardening, cracking, and rotting. Serious overheating may be caused by old radiator hose collapsing, or shedding rotted rubber that clogs the radiator core and is very difficult to remove. Swelling of hot-water heater hose may cut down the flow so that car heating becomes unsatisfactory. Hose without fabric reinforcement may break without warning and cause sudden, large cooling liquid losses and serious overheating. No dependence can be placed on outside inspection of cooling-system hose. (See fig. 16.)
C-7. ENGINE WATER-JACKET JOINTS AND GASKETS
Wide changes in temperature, normally occurring when an engine is warming up and cooling down, especially in winter, impose strains on all gasket joints. In addition, gaskets deteriorate with time, and corrosion occasionally develops in metal joints, such as core-hole plugs. Any leakage in waterjacket joints is aggravated by pump pressures which may run as high as 35 pounds per square inch.
Leaky core-hole plugs should be replaced immediately. Before installing a new plug, clean the core-hole seat and coat it with a suitable sealing compound. Use the recommended tool for driving the new plug in placp. Merely tightening the bolts on thin water-jacket cover plates may start leakage, if it does not already exist, by bending the plate under the bolts and breaking the old gasket. .
All outside water-jacket-gasket joints should be checked for tightness at least every 30 days or 1,000 miles. This also applies to thermostat and pump-
housing gaskets. When installing new gaskets, thoroughly clean the metal contact surfaces and apply a suitable sealing compound to the gasket unless otherwise recommended by the vehicle manufacturer.
Drainplug leakage should be corrected immediately by tightening, or applying a nonhardening * sealing compound to the threads. Drain cocks which no longer close tightly usually require replacement. (See fig. 4.)
C-8. CYLINDER-HEAD-GASKET JOINTS
There are actually about 20 individual joints in the water transfer holes between the cylinder head and block of a 6-cylinder engine, the looseness of any one of which will allow unobserved leakage of liquid into the cylinder or leakage of exhaust gas into the cooling system. The cylinder-head joint is not only subjected to the strains of normal temperature changes in the engine, but also to explosion pressures as high as 600 pounds per square inch. Besides the serious injury which may be caused by cooling-liquid leakage into the engine, exhaust gas blown into the cooling system forms acids which cause corrosion damage to cooling-system metals, as well as rapid rust formation and radiator clogging. Considering the' seriousness of the trouble or damage that may result from cylinder-head-gasket leakage, more thought should be given to preventive servicing of the cylinder head.
The statement of the old-time mechanic that he can properly tighten a cylinder head with an ordinary wrench by feel has long since been disproved by checking his work with a tension-indicating wrench. Cylinder heads can be tightened too much as well as too little and excessive tension may distort the block casting at valve seats and cylinder bores, permitting piston blow-by and valve leakage that seriously affect engine performance and life.
After a cylinder-head joint has once been properly serviced and tightened, the hold-down bolts or nuts
Figure 17—Exhaust gas leaking into cooling system at cylinder-head joint.
11
should be checked at least every 5,000 miles with a tension-indicating wrench. Special attention should be given to tightening bolts or nuts which hold down horns or other accessories subjected to vibration. However, tightening does not always correct leakage already existing and, if there is a suspicion of head-joint leakage, it is safest to replace the gasket after thoroughly cleaning off the joint surfaces and using a gasket compound recommended by the factory. Leaky studs should be removed and the lower threads treated with a suitable sealing compound, while upper stud threads should be lubricated. When the cylinder head is removed for any reason, check the gasket surfaces of the head and block with a straightedge and reface the surfaces if necessary. Never use the old gasket again and always be sure that the new replacement gasket is the correct one and is properly installed. Follow factory instructions on head bolt tension and on the order of tightening bolts. (See fig. 17.)
C-9. WATER PUMP AND FAN
According to the chemical formula, iron plus water plus air equals rust. When air is drawn into the cooling system through a leak at the pump seal, this air mixed with the cooling liquid may speed up rust formation as much as 30 times and greatly increase corrosion of all metals. Clogging and corrosion go hand-in-hand with chronic water-pump leakage and aeration. Entrainment of air in the cooling liquid also reduces heat transfer and therefore may raise engine temperatures and even bring about overheating at high engine speed and output.
If, in the old, adjustable gland-type pump, tightening the packing nut or replacing the packing does not correct the leakage, a worn shaft or bearing may be the real trouble and should be replaced. In the newer packless pumps no adjustments can be made for leakage. This self-adjusting type generally .has two seals, a composition or rubber seal on the shaft and a fibre, carbon or metal thrust seal which bears on either the housing or impeller hub and is held in place by a compression spring. Air suction through a perforated rubber seal can result in serious overflow loss and shortage of liquid in a few miles of highspeed driving. The thrust seal and its seat are subject to wear and leakage. Liquid leakage, if not promptly corrected, will in turn destroy lubrication, resulting in corrosion and wear of shaft and bearings. Thrust seals are prematurely worn by the abrasive action of rust in the cooling liquid and by operation in an overheated engine. (See fig. 7.)
Pumping failures are generally found to be due to a worn or loose fan belt, pump impeller loose on shaft, edge-wear of impeller blades, or pump housing worn away. A solid freeze-up may cause shearing of the impeller pin. Impeller blades sometimes are worn away by the combined effects of corrosion and ero
sion in cooling systems where rust prevention has been neglected.
To evaluate the pumping pressure, a rough check for cooling liquid circulation is made by compressing the upper hose by hand with the engine running at about 1,000 r.p.m. at driving temperature, with thermostat wide open. Another indication of pumping
Figube 18.—Suction of air into cooling system.
action is also obtained under the same conditions by observing the velocity of the liquid entering the top radiator tank, if visible through the filler opening.
For proper lubrication, adjustment, repair or replacement of fan, fan belt, and water pump, the factory instructions should be followed. This applies particularly to proper assembly of the pump seal parts, which otherwise will allow leakage to continue. Comparatively few water pumps are any longer driven from the generator shaft and many pumps now have self-lubricated sealed ball bearings. (See fig.' 18.)
C-10. THERMOSTATS
Automatic control of engine-operating temperatures is generally accomplished by a thermostatically operated valve in the water line between the waterjacket outlet and the top tank of the radiator, although there is a limited use of thermostatically operated radiator shutters.
For efficient and economical operation and for long life, automatic control of engine operating temperatures is absolutely necessary summer and winter. Minimum thermostatically controlled coolant operating temperatures range from 140° to 180° F., measured at the water-jacket outlet. Maximum coolant temperatures may run considerably higher.
Low operating temperatures during cold weather may result in overcooling of the engine with excessive gasoline consumption, water-oil sludge formation, and wear or corrosion of moving parts. Lubrication failure and serious engine damage will follow clogging of oil screens and lines. Excessively high operating
12
temperatures cause break-down of the lubricating oil and formation of deposits. Some of the penalties of overheating are sticky valves and piston rings, wear and damage to bearings, pistons and cylinder walls,
Figure 19.—Damaged thermostat.
cracked cylinder heads or blocks, and even engine seizure.
Testing of water-line thermostats should receive more frequent attention in view of serious overcooling and overheating damage that can follow their failure. Vehicles should never be driven with the thermostat out of order or removed. Overheating from any cause may damage the thermostat so that the valve will always stand open, allowing the engine to run too cool; or the valve may not open properly, causing further overheating. The moving parts are subject to wear and rust interferes with operation. The thermostat should always be checked after overheating has been experienced.
High-temperature thermostats with a start-to-open rating of at least 160° F. are recommended for improved engine performance and better heat from car heaters during cold-weather driving. The use of two thermostats in the same water line, connected in tandem, introduces an unnecessary complication and should be avoided if possible, as it may cause overheating and overflow loss. High opening thermostats usually eliminate the use of alcohol antifreeze because of its low boiling point. (See fig. 19.)
C-ll. RADIATOR COVERS AND MANUALLY OPERATED SHUTTERS
In certain types of vehicle service, particularly multiple-stop driving, thermostatic control does not always maintain satisfactory operating temperatures during winter weather, with the result that the engine is subjected to the hazards of overcooling previously mentioned.
To avoid cold-engine operation under these conditions, manually operated radiator shutters and adjustable radiator covers are commonly employed. When using such radiator covering, the driver must be watchful to adjust them properly for rises in air temperature or overheating will take place.
0-12, THERMOSTAT TESTING
Water-line thermostats should be removed and tested at least once a year or every 10,000 miles and whenever the system is opened for inspection or cleaning. A simple shop method for testing thermostat operation follows: Hang the thermostat by its frame in water heated 10° F. to 15° F. above the rated start-to-open temperature. If the valve fails to open, the thermostat should be replaced. However, any mechanical irregularities in the operation of the valve due to water flow or pressure must be checked in the car under service conditions. Service tests should also be made on the thermostat unit and mechanical linkage of automatic radiator shutters. (See fig. 20.)
Figure 20.—Simple shop test for checking thermostat operating unit.
C-13. THE EFFECT OF ALTITUDE ON THERMOSTAT OPERATING TEMPERATURES
Factors affecting thermostat operation in service are liquid temperature, head, flow and pressure, size of valve vent hole, and balance of the stat. Bellows-type thermostats are also affected by altitude. Still-water tests at reduced air pressures, correspond-
13
ing to altitudes above sea level, indicate that the opening temperature of the bellows-type thermostat may drop about 2.5° F.at 2,000 feet elevation,4.5° at 3,000 feet, and about 9° at 5,000 feet, the elevation of Denver, Colo. The bimetallic spring-type thermostat is not similarly affected because it depends on the expansion of a bimetallic spring to provide the force which opens the valve.
While the bellows-type thermostat may have a tendency to slightly lower cooling liquid operating temperatures at higher altitudes under some driving conditions, it is also true that the boiling point of the liquid drops to about the same extent, so that the margin of safety between the boiling point of the liquid and its operating temperature is maintained. The operation of the bimetal type thermostat does not compensate for reduced boiling points resulting from higher altitudes, so that any drop in boiling point theoretically should reduce the margin of safety. However, no service data are available to establish whether the effect of altitude on thermostat operation is more than a theoretical consideration.
C-14. WATER DISTRIBUTION TUBES
In the more recent models, the engine has a sheetmetal tube located lengthwise in the water jacket for the purpose of obtaining more uniform cooling and to prevent localized hot spots. Through openings in the tube, cool water from the pump is directed towards the exhaust valve seats. In its proper position, this tube receives the full delivery of the pump into the water jacket. When the water-distribution tube is out of position or perforated by corrosion, improper circulation of the cooling liquid will cause local overheating and valve trouble and even heat
cracking of the engine block or head. In overheating cooling systems, where corrosion prevention has been neglected, water-distribution tubes and manifolds have been found perforated by corrosion.
On account of the importance of the water-distribution tube to the proper cooling of the engine, the tube should be inspected at least once a year or every 15,000 miles. This can be done without removing the radiator by taking off the water pump, pulling out the tube part way, and using aflashlight and mirror. If the water tube is removed, a good opportunity is afforded to inspect the inside of the water jacket. As a matter of precaution, waterdistribution tubes should be replaced at engine overhaul periods. (See fig. 21.)
D.	DIAGNOSIS OF OVERHEATING AND
OVERCOOLING OF ENGINE
Frequent check of the heat-indicator gauge should be a fixed habit with vehicle drivers. One large fleet operator reports experiments with a thermostatically, controlled and electrically operated bell in the driver’s compartment as an audible warning of overheating. Any appreciable deviation from the normal heat indication, either high or low, should be reported at the first opportunity, preferably in writing on a “Driver’s Daily Report.” Following. such a warning, there should be no delay in inspection to determine the cause or in necessary servicing to correct it. Con-. stant alertness on the part of the driver with regard to engine-operating temperatures can do much to forestall many serious operating difficulties which are \ indicated by the first stages of overheating or overcooling of the engine. However, the possibility of a false temperature indication, due to failure of the
Figure 21.—Showing coolant flow through distribution tube.
14
heat-indication unit or the gauge, should not be overlooked.
Overheating can result from any one of a number of conditions or from a combination of several. Often itself. According to the experience of one overland the cause of overheating is not in the cooling system fleet operator, improper fuel mixture and valve or
Figure 22.—Damage caused by overheating: Left, burnt valves; right, scored piston.
ignition timing are the most common causes outside of the cooling system.
The outline which follows is designed as a guide for quick diagnosis of overheating and overcooling, as related to causes both within and outside of the cooling system. (See figs. 22 and 23.)
Figure 23.—Damage caused by overcooling: Left, corroded piston; right, corroded wrist pin.
D-l. DIAGNOSIS OF OVERHEATING
1.	LOW LIQUID LEVEL IN COOLING SYSTEM
A.	Leakage of system
1.	Water hose, radiator, and car heater:
a.	Loose or defective hose clamps and fittings.
6.	Defective rubber hose.
2.	Radiator and hot-water heater:
a.	Cracked seams, core, tanks, and overflow pipe.
b.	Broken joints in outlet or inlet fittings.
c.	Tanks or core worn through at points of support.
d.	Corrosion perforation of water tubes.
e.	Loose or defective drain-cock, plug, or vent.
f.	Accidental damage.
3.	Engine block water jacket:
a.	Loose or defective drain-cocks or plugs.
b.	Loose or corroded core-hole plugs.
c.	Cover plates loose or gasket defective.
d.	Corrosion-perforation of cover plates.
e.	Water bypass connections loose.
f.	Defective car heater shut-off valve.
g.	Pump housing loose or gasket defective.
h.	Warped block at cylinder-head joint.
i.	Cracked or porous water-jacket casting.
j.	Loose or broken joints in water-cooled oil radiators or lines.
k.	Cylinder-head studs loose in block.
I.	Deteriorated wet cylinder-sleeve seals.
4.	Cylinder head:
a.	Defective or blown gasket.
b.	Loose hold-down bolts or nuts.
c.	Cracked, porous, or corroded head casting.
d.	Head casting warped at block joint.
e.	Loose thermostat housing or defective gasket.
/. Loose heat-indicator fitting.
g.	Loose heater-hose nipple.
h.	Corroded, broken, or loose water manifold.
i.	Loose or corroded core-hole plugs.
5.	Water-pump shaft seal:
a.	Worn-out packing, or loose nut, in gland type.
b.	Scored shaft or worn bearing, in gland type.
c.	Scored, worn, or warped thrust seal, in packless type.
d.	Deteriorated or perforated' shaft seal, in packless type.
e.	Thrust-seal compression spring failure, in packless type.
f.	Scored or corroded shaft, in packless type.
g.	Worn or corroded bearings, in packless type.
B.	Overflow loss of cooling liquid
1.	Steam formation at hot spots in water jacket.
2.	Air entrainment from radiator top tank turbulence.
3.	Air suction into cooling system.
4.	Coolant surge from pump action and vehicle motion.
5.	Foaming of cooling liquid.
6.	Defective radiator baffle plate.
7.	Two water-line thermostats in tandem.
8.	Exhaust gas leakage into cooling system.
9.	Use of alcohol antifreeze with high-opening thermostat.
15
10.	Use of alcohol antifreeze for high-altitude driving.
11.	Failure of vacuum in system with radiator overflow tank.
12.	Corrosion perforation of overflow tank.
13.	Loose radiator cap, or cap missing.
14.	Pressure valve in radiator cap stuck open.
15.	Restricted flow in radiator core.
2.	OBSTRUCTED OR INADEQUATE COOLING LIQUID CIRCULATION:
a.	Rust-clogged radiator core.
6.	Rust-clogged water jacket passages.
c.	Thermostat valve stuck in closed position.
d.	Bypass valve stuck in open position.
e.	Collapsed radiator hose, or torn and loose lining.
j.	Slush ice freeze-up in radiator core.
g.	Water-pump impeller loose on shaft.
h.	Pump-impeller blades corroded, worn or broken housing interior corroded.
i.	Failure or slippage of pump drive.
j.	Shortage of liquid from incomplete filling of system.
k.	Water-jacket distribution tube corroded through or out of position.
I.	Liquid capacity of system reduced by rust deposits.
3.	OBSTRUCTED OR INADEQUATE AIR CIRCULATION:
a.	Fan belt worn or loose.
b.	Fan blades bent.
c.	Improper fan equipment.
d.	Radiator air baffles out of place.
e.	Clogged bug screen.
y. Radiator air passages clogged with dirt, bugs, etc.
g.	Hood louvers defective or closed.
h.	License plate or similar obstruction mounted in front of radiator.
i.	Manual radiator shutters left closed.
j.	Radiator cover not properly adjusted.
k.	Automatic shutters not functioning properly.
4.	EXTERNAL CAUSES SOMETIMES CONFUSED WITH COOLING SYSTEM:
a.	Engine timing delayed or advanced.
b.	Improper fuel mixture.
c.	Lubrication system clogged with oil-water sludge in overcooled engine.
d.	Lubrication failure from freezing of water in oil screen.
e.	Oil breakdown deposits in engine, valves, and piston rings sticking.
y. Shortage of engine oil.
g.	Exhaust line thermostat out-of-order.
h.	Clogged exhaust muffler or line.
i.	Engine in bad mechanical condition.
J.	Dragging brakes.
k.	Excessively high, sustained speed.
I.	Overloading |of vehicle.
m.	Traveling with tail wind under heavy load. n. Driving in deep sand, mud, or snow.
D-2. DIAGNOSIS OF OVERCOOLING
1.	Thermostat:
a.	Not installed, or removed.
b.	Valve stuck in open position, or fails to close. c. Valve-opening temperature too low.
d.	By-pass valve stuck in closed position.
e.	By-pass line clogged or blocked off.
2.	Stop-and-go (multiple stop) driving at low engine speed and output.
3.	Thermostatic control fails to maintain adequate engine-operating temperature.
E.	COOLING SYSTEM CORROSION AND ITS PREVENTION
Rust-proofing of the cooling,system in winter can be accomplished automatically through the use of standard antifreeze products containing corrosionpreventing ingredients called inhibitors. However, judging from the limited use of corrosion inhibitors with water, it is apparent that many vehicle operators do not fully appreciate that the corrosion problem is even more serious in warm weather because of higher operating temperatures and aeration rates prevailing with the thermostat valve wide open and with maximum liquid flow and turbulence in the radiator.
The discussion of cooling system corrosion which follows is based on tests with laboratory corrosion apparatus, engine dynamometers, and vehicle driving service. Since water is the standard cooling liquid around which most automotive engihes are designed, a review of the corrosive effects of normal and incidental contaminants in water should give the vehicle operator a better understanding of the need for rustprevention treatment.'
The common water contaminants causing corrosion of cooling system metals are oxygen from the air, dissolved minerals in natural water supplies, acids from exhaust gas leakage into the system, residual chemicals in the water jacket or radiator, undrained and unneutralized cleaning solution, inorganic salt antifreezes, and some stop-leak preparations. Corrosion is also a function of the composition, location and proximity of various cooling system metals. Electrolytic corrosion is stimulated by combinations of different metals in contact with each other, as in alloys, soldered and brazed joints, metal gasket joints and imperfect lead or copper plating on thin steel parts.
16
E-l. AERATION OF THE COOLING LIQUID
No cooling system is free of air and oxygen from the air is the most prevalent and serious factor in promoting corrosion in any type of water. For example, m typical water supplies, such as the Great Lakes, aeration of water can increase corrosion of iron 30 times. In more corrosive mineral waters, the effects of aeration may be more severe. Even in distilled water, the effects of aeration on corrosion are marked, especially with iron and solder. Since air entrainment and aeration of the cooling liquid take place during engine operation and usually increase with engine speed, the corrosive effects of oxidation are relatively greater as vehicles are driven more miles and at higher speeds.
Even in leak-tight cooling systems, entrained air during normal engine operation may exceed 1 percent of the total volume of the cooling system. There are two principal causes of aeration in a leak-tight system. Turbulence of the cooling liquid in the top tank of the radiator produces air entrainment which increases as the liquid level drops. In addition, when the level drops to or below the top of the water tubes, pump suction becomes a serious problem in that air in large quantities is drawn in through the radiator overflow pipe and down through the water tubes.
E-2. MINERAL SALTS IN NATURAL WATER SUPPLIES
The corrosiveness or noncorrosiveness of natural waters in cooling system service cannot be accurately predicted in any particular case from analysis of the water. Various mineral salts occurring in the water may have a neutralizing action on one another or they may all increase corrosion. Neither can any particular interpretation regarding corrosion be placed on the total dissolved solids found. Furthermore, even in ground or well water supplies the mineral salt content varies somewhat with rainfall, while in surface waters, as from lakes and rivers, the variation in mineral content is even greater. It has been estimated that the usage of well and surface waters is about equally divided on the basis of population, the smaller communities and rural districts being supplied principally with well water of higher mineral salt content.
The common mineral salts found in natural waters and which stimulate corrosion are chlorides and sulphates in combination with calcium, magnesium, and sodium. Chlorides are by far the most active and as little as 200 parts per million is quite likely to stimulate corrosion. The effect of either sulphates or chlorides or mixtures of both is generally characterized by local pitting and sometimes perforation of metal parts, although metal weight losses may be comparatively low. The degree of attack on differ
ent metals is erratic and unpredictable. Several deep-well waters were found to contain from 200 to 500 parts per million of chlorides or chlorides plus sulphates. High-saline well waters are difficult to inhibit in comparison with surface waters and inhibition is not as effective as in waters relatively free of mineral salts.
The average sulphate and chloride contents of 12 large surface water supplies located across the country were 38 parts per million and 13 parts per million, respectively, and the average hardness 103 parts per million. In general, it appears that surface waters containing up to 170 parts per million hardness, 90 parts per million sulphate, or 45 parts per million chloride will have similar corrosion characteristics in the cooling system. Apparently, chloride and sulphate content in the range of 10 to 100 parts per million will not greatly influence corrosion.
In surface waters, the average corrosion weight loss of nonferrous cooling system metals (aluminum, brass, copper, and solder) was only 2 percent that of iron, and in saline well waters 10 percent, the latter due to the increase in nonferrous loss and decrease in iron loss with high saline content. However, the danger of embrittlement, pit corrosion, and perforation should not be minimized in nonferrous metals because of the low weight losses.
Acidity in natural waters (pH below 7.0) accelerates iron corrosion and rust formation, while alkalinity reduces attack on iron. Decomposition of vegetable and animal matter in water will produce acidity. Waste chemical matter from factories or plants may produce either acidity or alkalinity. Aerated distilled water may be as corrosive to brass and more corrosive to iron, copper, and solder than some high-saline waters.
E-3. INCIDENTAL CONTAMINANTS
1.	Residual zinc-chloride solder flux in the radiator or ammonium chloride sometimes used for sealing porous water jackets can cause serious corrosion in quantities as small as 100 parts per million in the cooling water.
2.	Unneutralized acid-cleaner solutions as well as alkaline-cleaner solutions left in the system after use may also accelerate corrosion of various metals. Vehicle operators are cautioned about the use of hydrochloric (muriatic) acid as a cooling-system cleaner because of the high corrosion rate of chlorides.
3.	Stop-leaks should be selected with care because of possible organic acid content when installed or the development in service of acidity and possibly corrosion through decomposition of stop-leak ingredients.
4.	Exhaust gas leakage into the cooling system contaminates the cooling liquid with various acids which accelerate rust formation and corrosion.
5.	The corrosive effects of inorganic salt antifreezes such as calcium and magnesium chlorides
17
are unfortunately well known to a large number of vehicle owners, who unwittingly purchased them as substitutes for safe organic antifreezes.
E-4. EFFECT OF TEMPERATURE ON CORROSION
With the use of surface waters, the rate of corrosion with iron appears to reach the maximum at coolingliquid temperatures corresponding to best engine performance. Aluminum seems to be susceptible to the greatest attack at slightly higher coolingsystem temperatures. From a temperature rise from 70° to 175° F. the rate of iron, copper, brass, and solder corrosion more than doubles. Laboratory test results indicate that higher engine-operating temperatures during warm-weather driving speed up corrosion and rust formation.
*
E-5. TYPICAL CORROSION DAMAGE OF COOLING-SYSTEM PARTS
Among the cooling-system metal parts commonly damaged from corrosion of the cooling liquid when rust-prevention treatment is neglected are radiator cores and caps, water pumps, cylinder heads, water-
Figure 24.—Corrosion of radiator water passage metal.
Figure 25—Water pump impeller corrosion.
jacket cover plates, core-hole plugs, water-distribution tubes, and manifolds. (See figs. 24, 25, 26, and 27.)
Figure 26—Corroded water distribution tube, showing irregular corrosion holes.
Figure 27 — Section of aluminum head showing corrosion damage.
E-6. TREATMENT OF COOLING WATER FOR CORROSION PREVENTION
A coating of rust in the water tubes of the radiator or on the heated surfaces of the engine inside the water jacket will interfere with heat transfer even when very thin. If cooling of the engine is to be maintained at new-car efficiency, rust deposits must be prevented from forming. Likewise, corrosion of iron and other cooling-system metals must be reduced to a minimum if replacement of parts from corrosion damage is to be avoided. Suitable treatment of water for corrosion prevention will reduce rusting of iron at least 95 percent. Rust inhibitors for water are inexpensive and simple to use and make cleaning and flushing unnecessary for long periods of driving. Cooling-system rust prevention is strongly recommended by vehicle factories.
Large fleet operators report reduction of coolingsystem rust-clogging and corrosion damage after using corrosion inhibitors with water. One operator states from his experience that treatment of water for rust prevention prolongs the life of the engine and radiator regardless of operating conditions. Another reports that in years of use of rust inhibitors in a large fleet only two radiators had to be replaced and both were in accidents.
There are two types of water inhibitors in general use—soluble oils and salts. For best results, both types should always be used in the proportions recommended by their manufacturers. Corrosion inhibitors do not remove rust already formed in the
18
system, and any necessary cleaning out of rust should be performed before the inhibitor is installed. Standard antifreeze products contain corrosion inhibitors and it is therefore not necessary or desirable to add extra inhibitor to fresh antifreeze solutions. Mixing different types of inhibitors in the cooling system and the use of inhibitors that cause foaming and overflow loss should be avoided.
Treatment of water for rust prevention can best be accomplished in the cooling system itself. Starting with the system clean, simply fill it nearly full with fresh water and add the recommended dosage; then operate the engine until it reaches driving temperature to open the thermostat and establish circulation through radiator and engine block for complete mixing.
Where antifreeze is used, drain the solution in the spring after freezing weather is past; flush the system thoroughly and clean if necessary; then install a fresh filling of summer rust inhibitor and water. If leakage and overflow loss of inhibitor solution are kept down to a minimum, one treatment should be effective for the warm weather driving season. If antifreeze is not used, add a dosage of rust preventive to a fresh filling of water both spring and fall.
Inhibitor treatment of water prevents corrosion and rust formation by chemical action and by depositing a thin protective film on the inside walls of the cooling system. In a system that was clean originally, the appearance of rust in the radiator or in solution is an indication that the inhibitor is weakened from adding water or is exhausted from use. In either case, the solution should be drained, the system flushed, and a fresh filling installed.
F. COOLING SYSTEM CLOGGING AND METHODS FOR CLEANING
Although engine overheating from clogging of the cooling system was found in a recent survey to be the cause of over 12 percent of all cooling system troubles, this difficulty can be avoided entirely by preventive cleaning and regular rust-proofing. Analyses of clogging materials removed from radiators and water jackets show them to be made up mostly of iron rust, water scale and grease, with iron rust comprising over 90 percent of the bulk. Grease and oil may enter the system through the water pump and through leaks at the cylinder-head joint or in water-jacketed oil coolers and lines. The amount of rust or other materials that will clog a radiator is much smaller than is generally realized. Enough rust to fill the top quarter-inch of the water tubes will cause serious restriction of water flow.
The rate of corrosive attack of untreated water on iron is invariably higher than on other cooling system metals. In the average surface water supply, corrosion weight loss of iron is found to be over ten
times as great as the total weight losses of aluminum, copper, brass, and solder for the same surface area. Considering this fact, as well as the comparatively large iron surface exposed in the water jacket and other parts of the cooling system, it can be readily appreciated why iron rust is the principal problem in the loss of heat transfer and in the clogging of radiators and water jackets. Besides reducing heat transfer and restricting circulation, another deleterious effect of rust is to shorten the noncorrosive life of antifreeze solutions.	•
The main source of cooling system rust is the engine water jacket, where the rust is formed on the iron surfaces. Liquid circulation keeps loosening the rust as it forms and the larger rust scales usually settle in the water jacket. However, the finer particles are carried over into the radiator where they becomfe attached to the inside walls of the water tubes and tanks in the form of a hard, adherent scale.
A year or more is usually required for the rust layer in the radiator tubes to become thick enough to seriously restrict circulation, but in the meantime the scale accumulations continue to reduce the cooling efficiency of the radiator until the engine finally overheats. Resultant boiling stirs up the rust deposits which have been growing in the water jacket and circulation carries large quantities over into the radiator. After boiling starts, only a short period of operation is needed to load the radiator tubes and practically stop circulation. Then further driving is out of the question until both the radiator and engine block receive corrective cleaning service. (See fig. 10.)
F-l. WATER-SCALE FORMATION
Although the formation of lime and other mineral scale from water is generally considered a minor factor in cooling system deposits, a brief discussion of the subject may be of value to vehicle operators located in hard water areas. The total amount of dissolved solids in natural waters is not a reliable indication of the scale forming ability of the water, although total hardness as to calcium carbonate may be used as an index of scale formation. Calcium and magnesium are the chief metal constituents in the hard-water scale. Excessively large amounts of calcium and magnesium carbonates and bicarbonates may lead to undesirable water-scale formation if large quantities of the hard water are constantly being added to the cooling system over a long period of time to replace leakage or overflow losses. Silica with large amounts of calcium or magnesium carbonate forms a particularly tenacious water scale. Rain water contains no scale forming minerals.
With large additions of water and with high driving mileages, scale formation should be noticeable in water containing more than 500 parts per million of either calcium or magnesium or both. The average
19
hardness of 12 surface-water supplies was found to be 103 parts per million. Hardness* in water varies with rainfall and the variation is especially great in surface waters. For instance, samplings from the Mahoning River at Youngstown, Ohio, showed a 44 percent change in hardness during a 5-day period.
Water from some localities contains dissolved mineral salts that precipitate and form scale with evaporation of the water; or scale may be formed by simply heating the water without boiling. Even in extremely hard water, however, the actual quantity of mineral salts that, would produce scale is very small, especially as compared to the amount of iron rust normally formed. Probably the chief problem with water scale is the formation of localized lime deposits at hot spots near exhaust valve seats or between cylinders, where continuous boiling may be occurring.
F-2. PREVENTION OF WATER SCALE
While several special commercial methods of softening cooling-system water have been reported in recent years, the practice has never gained more than limited use, according to available information. Lack of general interest in softening of radiator water may possibly be due to the absence of any real necessity for it except in certain local areas. Most watersoftening methods would introduce chemicals into the cooling system. In one case sodium chloride is used to regenerate the softener. Such chemicals complicate the problem of rust inhibition and may cause foaming and overflow loss. The following preventive service methods are suggested to minimize water-scale formation:
1.	Avoid excessively hard water wherever possible. Use soft or rain water whenever conveniently available. Water softening equipment has been used in some localities.
2.	Periodic preventive cleaning of cooling system to remove rust formations that would cause hot spots and local boiling.
3.	Keep water additions down to an absolute minimum by eliminating overfilling and by a preventive maintenance program that will keep leakage and overflow losses down to a minimum.
4.	Always use a corrosion inhibitor with water.
F-3. PREVENTIVE CLEANING OF THE COOLING SYSTEM (CHEMICAL)
Formerly nearly all radiator cleaners were of the alkaline type, such as washing soda, or were organic solvents, such as kerosene. Although these materials cut grease and remove loose rust deposits, they are not entirely effective, since they have no solvent action on the rust itself and therefore do not remove hard scale in the radiator core or water jacket. A suitable cooling system cleaner must be capable of
removing adherent scale by dissolving action. Oxalic-acid and sodium-bisulphate types of cleaners have been found satisfactory in this respect and are specified by the U. S. Army. An acid cleaner should preferably be inhibited to reduce cooling system corrosion to the minimum consistent with effective cleaning.
F-4. PREVENTIVE CLEANING PROCEDURE
1.	Completely drain the system, put in the recommended amount of acid cleaner and fill with fresh water. With the radiator covered, run the engine at least 30 minutes with the solution hot (at least 180° F. but below boiling). Stop engine and after a few minutes thoroughly drain the system. Because of the danger of overflow loss from foaming, do not drive the car with cleaning solution in the system.
2.	Pom the recommended amount of neutralizer into the radiator, fill with water and run the engine until warmed up to driving temperature in order to circulate the neutralizer solution throughout the system and completely end all action of any undrained cleaner solution.
3.	Flush the radiator and water jacket thoroughly with water to complete the cleaning operation before the car is driven. Do not leave the neutralizer in the system, since it is not a rust inhibitor.
4.	After cleaning and flushing, check the thermostat; also clean out the overflow pipe and lubricate the water pump, if necessary, and blow insects and dirt from radiator air passages, grilles, and bug screen. In sealed cooling systems be sure that the valves in the radiator cap are free from sediment and properly seated.
F-5. PREVENTIVE FLUSHING PROCEDURE
In the simplest method of flushing the cooling system, the drain cocks are opened, and with the engine running at lower speed, the radiator is kept-filled by a stream of water from a hose inserted in the filler neck. The objection to this method is that cold water from the hose may close the thermostat and prevent thorough flushing of the water jacket.
Following the use of a cleaning solution, a more positive method for removing cleaner from the water jacket is to completely drain the solution, fill with water, run the engine long enough to open the thermostat for complete circulation through the system, then completely drain the water.
For the most complete removal of loose rust from radiator and water jacket, pressure flushing with an air-and-water gun is to be recommended, but this method requires opening the hose connections and removing the thermostat. If there is a question about the effect of pressure flushing on the pump, follow factory instructions.
20
Periodic flushing with water may remove the loose rust, but is not effective for removal of hard, adherent rust scale. The use of an acid type cleaner is first necessary to loosen or dissolve the scale.
F-6. CORRECTIVE CLEANING OF THE COOLING SYSTEM (CHEMICAL AND MECHANICAL)
For cleaning clogged systems, follow the preventive cleaning procedure specified in section F-4, above, but increase the quantity of cleaning compound in accordance with the manufacturer’s directions and lengthen the engine running time as indicated by the condition of clogging. To avoid using excessive amounts of cleaner, time and gasoline that might be required to completely dissolve all accumulations, pressure flushing is recommended and is sometimes necessary in the final flushing operation to remove any loosened but undissolved rust remaining in the radiator or water jacket.
F-7. PRESSURE FLUSHING PROCEDURE
Facilities needed for pressure flushing are a special air-and-water flushing gun, designed for attachment to cooling system hose connections, and compressed air and water supplies with hoses for attaching to the gun. The radiator and water jacket are first reverse flushed, that is, in the direction opposite to the normal flow of cooling liquid; then flushed in the normal direction of flow. (See figs. 28 and 29.)
Figure 28—Cooling system flushing gun and special nozzle for heater.
Flushing Radiator.—With the hoses disconnected, the radiator cap on tight, and the flushing gun clamped on the lower radiator hose, turn on the water and let it run until radiator is full, then apply air pressure gradually to avoid radiator damage. Shut off the air, fill the radiator with water and again apply air pressure. Repeat the operation until flushing stream runs out clear. (See fig. 29.)
Flushing Water Jacket.—Remove the waterline thermostat, connect the flushing gun, and partly close the water pump opening to fill the
Figure 29.—Pressure flushing of radiator.
WATER HOSE ^FLUSHING GUN
Figure 30,—Pressure flushing of engine block.
Figure 31.—Pressure flushing of hot water heater.
engine with water before applying the air. Follow the procedure for flushing the radiator by alternately filling the water jacket with water and blowing it out with air (full pressure) until the flushing stream runs out clear. (See fig. 30.)
21
Flushing Hot-Water Heater.—Disconnect the heater hoses and flush in the reverse and normal directions in the same manner in which the car radiator was flushed. Apply air pressure gradually to avoid damage. (See fig. 31.)
F-8. SPECIAL CORRECTIVE CLEANING METHODS
1.	For flushing out water jackets containing excessively heavy rust-sludge deposits, remove the core-hole plugs or cylinderhead studs, and pressure flush directly through the holes with a small flexible tube attached to the flushing gun nozzle.
2.	In cases of very severe radiator clogging, the tubes may be so tightly plugged that the cleaning solution cannot reach all the clogging material. Such a condition usually requires the services of an experienced radiator repairman. One boil-out method used with good success for clogged radiators follows: (1) Remove radiator from the car; (2) close radiator inlet and outlet; (3) fill radiator with water; (4) add can of acid cleaner; (5) with the cap off and the radiator in an upright position over a gas flame keep the cleaner solution just at the boiling point until the rust is dissolved and loosened; then (6) neutralize the radiator; and (7) pressure flush.
3.	If boil-out methods fail, the last resort is to remove the radiator tanks and mechanically clean the water tubes, by rodding.
4.	Hydrochloric (muriatic) acid solutions are sometimes used for corrective cleaning badly scaled or rusted water jackets, particularly in rebuilt engines. One fleet operator reports completely dissembling the engine and closing all except top openings of the jacket. The acid is left in the block or head from 10 to 12 hours. Another operator, by means of special equipment, circulates heated acid through the water jackets with the engine assembled. Standard muriatic acid and other chemical solutions are used. Inhibited acid is reported to be highly desirable for reducing corrosive attack.
After draining the acid solution, neutralizing of the water jacket is necessary. Sodium carbonate in varying concentrations is reported to be used, followed by thorough flushing with water. Machined or polished surfaces must be carefully protected. In one case a heavy grease covering is employed for this purpose. Experience and care are highly important in the use of muriatic acid for water jacket cleaning, both from personal hazard and equipment standpoints. The supplier’s directions and precautions should be followed with care.
G. PHYSICAL AND CHEMICAL CHARACTERISTICS OF DIFFERENT TYPES OF ANTIFREEZE AND THEIR EFFECTS ON THE COOLING SYSTEM
In the cooling systems of water-cooled automotive engines, the water functions as a heat transfer medium, carrying heat from the water jackets of the engine to the car radiator where the heat is dissipated to the surrounding air. Only about one-third of the energy in gasoline used to operate a motor vehicle is converted into power, the remaining two-thirds being converted into heat. In conventional design, about one-third of this heat is carried off through the radiator, the remainder being dissipated through the exhaust and the outside surfaces of the engine.
Water is the natural selection for a cooling medium because of its relatively high heat transfer properties and availability. However, it has certain inherent disadvantages, the most important of which are its high freezing point and its corrosive action on the metal parts of the cooling system, which, if not inhibited, may result in corrosion damage and rustclogging. The essential requirements for acceptable antifreeze materials to be added to water are as follows:
1.	Ability to lower the freezing point of water to the lowest winter temperatures likely to be encountered.
2.	Incapability of imparting any undesirable properties to the water which would interfere with its primary function of efficient engine cooling.
3.	Satisfactory chemical stability in service and the ability to protect cooling system metals from the corrosive action of water.
G-l. RECOMMENDED ANTIFREEZE MATERIALS
Acceptable and commonly used antifreeze materials are ethylene glycol, ethanol (denatured ethyl alcohol), methanol (synthetic methyl alcohol), and isopropyl alcohol. Standard antifreeze products using any one of these materials also contain chemical ingredients known as inhibitors to increase their chemical stability and to prevent corrosion. AU these materials are organic and nonelectrolytic.
G-2. NONRECOMMENDED ANTIFREEZE MATERIALS
Oils, sugars, and inorganic salt solutions are un-satisfactory for one reason or another. The hazards
22
of using inorganic salts, such as calcium chloride, and petroleum oil distillates, such as kerosene, have received wide publicity recently from authoritative Government agencies and automotive experts and simple methods of testing to determine such unsuitable or deleterious compounds have been widely published.
The principal objections to inorganic salt antifreeze materials are electrical conductivity and corrosive effects. Leakage of salt antifreeze solutions onto the ignition system parts will cause serious shorting of electrical circuits. To date, no chemical treatment is known which will inhibit salt antifreezes against corrosion in the cooling system, even though they may produce satisfactory corrosion results in laboratory tests. Another objection reported on salt antifreeze is the possibility of crystal formation in the radiator which would restrict circulation.
Kerosene and similar oils are low freezing liquids, but cannot be used to depress the freezing point of water because they do not mix with water.
Because of their low heat transfer properties, oils are not suitable as coolants in engines designed for water cooling and under heavy load or at high speed serious engine damage from overheating can result from their use. Since oil vapors are inflammable, a very real fire hazard is presented when boiling and overflow of the oil occurs with overheating of the engine. Mineral oils have a solvent action on rubber and their use in the cooling system will result in rapid deterioration of rubber hose connections and rubber seals in water pumps.
Sugar solutions (including honey, molasses, etc.) may become excessively viscous at low temperatures and cause inadequate circulation and overheating in the cooling system. Charring of sugars will seriously interfere with heat transfer from the engine and charred deposits in the water jacket will present a most difficult cleaning problem.
PHYSICAL CHARACTERISTICS OF OR-
GANIC ANTIFREEZE SOLUTIONS
The discussion which follows on the physical and chemical characteristics of antifreeze solutions is confined to ethylene glycol, methanol and ethyl alcohol.
G-3. FREEZING PROTECTION
All three recommended types are capable of depressing the freezing point of water to the lowest temperatures likely to be encountered in vehicle driving. Methanol gives greatest freezing protection per gallon, ethylene glycol ranks next, and ethyl alcohol is the least effective. However, neither freezing protection nor price per gallon is a reliable guide for estimating coitiparative cost of using the different types. The correct basis of comparison is the over-
Chart I.—Freezing points of common anti-freeze solutions
all winter cost, including both the original filling and necessary additions. Freezing point curves for the commonly used concentrations of the three types are shown in Chart I.
Water freezes solid with 9 percent expansion in volume, which will cause breakage or bulging of the cooling system walls. Unlike water, antifreeze solutions do not solidify but tend to form slush at temperatures slightly below their freezing points. Laboratory tests in thin-w'alled glass tubes have shown that as little as 10 percent in water will prevent breakage damage from freezing at temperatures as low as 40° F. below zero. To explore the behavior of antifreeze solutions in the cooling system at temperatures below their initial freezing point, cold-room tests were made in which several popular vehicle models were chilled to low temperatures, following which the engines were started up and operated. Typical results from these tests are shown in Table I, indicating the range of mihimum safe temperatures to which solutions having zero degrees’ freezing point may be subjected without overheating or other difficulties developing from slush ice restriction in the radiator when the engine is operated immediately after chilling.
Since the minimum safe exposure temperature below the freezing point varies with antifreeze materials and solution concentrations, as well as with the design of the cooling system, the only safe recommendation
23
for installing antifreeze protection is on the basis of the initial freezing point of solution. The published freezing protection tables furnished with standard antifreeze products should be followed in determining the amount of antifreeze necessary in any given size of cooling system for the protection desired.
Table I.—MINIMUM SAFE TEMPERATURES OF ANTIFREEZE SOLUTIONS
Antifreeze	Freezing point	Minimum temperature
Methanol	 _ 		0° F.	—2.5° to -5.5° F.
Ethanol 				0° F.	-5.5° to -8.0° F.
Ethylene glycol		„		0° F.	-8.0° to -11.5° F.
When using antifreeze, the hazard of underprotection is overheating and heat-cracking, not freeze-cracking.
G-4. BOILING POINT CHARACTERISTICS
Automotive engines are designed to be operated without boiling of water withm the recommended limits of speed and load. It is obvious that if cooling liquid temperatures rise above the boiling point of the liquid, the natural result will be overflow losses and overheating from liquid shortage in the system. As a rough indication of cooling liquid temperatures in ordinary driving, attention is called to the range of rated thermostat valve opening. temperatures for 35 vehicle models of 1940 and 1941 make, shown in Table II.
Table IL—OPERATING TEMPERATURES OF FACTORY-INSTALLED THERMOSTATS IN 1940 AND 1941 OARS
Number of makes and models	Opening temperature, °F.
1	Below 145°.
6	145°-150°.
14								150°-155°.
14	□	l			155°-160°.
It should be pointed out that these opening temperatures represent only minimum theoretical solution temperatures, since the rated wide-open thermostat temperatures in those models vary from 170° to 185°, and therefore the actual liquid temperatures in normal cooling system operation will lie between the opening and wide-open temperatures. To the temperatures indicated above, upwards of 20 degrees must be added for the normal temperature rise in the cooling liquid immediately after stopping the vehicle. If boiling and its attendant troubles are to be avoided, the maximum solution temperature reached after stopping the vehicle or engine must be below the boiling point of the solution.
As a guide for selecting the type of antifreeze best adapted to maximum cooling liquid operating
temperatures, in any particular vehicle or fleet, the figures in. Table III, giving the boiling points at sea level of the three different types, for freezing protections from +10° to —20° F., should be of value to the vehicle operator. It will be noted that the solution boiling points of methanol and ethanol types are lowered with increase of concentration and freezing protection, while in the ethylene-glycol type the solution boiling point raises with higher concentration and increased freezing protection. In the freezing protection range of +10° to —20° F., the boiling points of ethylene-glycol solutions are 28° to 43° higher than the alcohol solutions.
Table III—BOILING POINTS OF COMMERCIAL ANTIFREEZE SOLUTIONS (°F.)
	Boiling points of solutions—			Freezing at —20°
	+10°	0°	—10°	
Methanol type	■	 Ethanol-type	,	 Ethylene glycol type.		Degrees 190 187 218	Degrees 185 184 220	Degrees 182 182 221	Degrees 179 180 223
The boiling point of water is lowered by additions of ethanol and methanol and raised by additions of ethylene glycol in proportion to the amounts added. Graphically illustrated in figure 32 are the sea-level atmospheric boiling points of water and of ethyleneglycol and alcohol solutions giving protection to
ANTI-FREEZE SOLUTIONS PROTECTING TO -20°F.
HATER
FREEZES AT +32°F.
Figure 32.—Sea-level atmospheric boiling points of water and of antifreezes giving protection down to — 20° F.
—20° F. Methanol, ethanol and ethylene-glycol antifreeze products are commonly distributed in • concentrations of approximately 94 percent to 99% percent. The boiling points of concentrated products should not be confused with the boiling points of commonly used solutions which rarely exceed 50 percent concentration even in the coldest areas of the country. Alcohol solutions cannot usually be
24
used with thermostats opening at 160° F., or higher, unless the cooling system is equipped with a pressure valve or surge tank (radiator overflow tank).
G-5. EFFECT OF ALTITUDE AND PRESSURE ON BOILING POINT
The boiling point of water and antifreeze solutions drops about 2° F. for each 1,000-foot rise in elevation, which of course increases the possibilities of boiling and overflow loss with high altitude driving. On the other hand, radiator-cap pressure valves in sealed cooling systems raise the boding point of water and antifreeze solutions. For example, in an airtight system with a pressure valve which opens at 5 pounds pressure, the boiling point of the cooling liquid may be raised 13° to 15° F.
G-6. FOAMING TENDENCIES OF COOLING LIQUIDS
Air entrainment in the cooling liquid is a condition which may occur during operation at higher speeds and, if excessive, may cause overflow loss of water or of any antifreeze solution. Some natural and contaminated waters have a greater tendency to foam than others. This does not refer to the head of foam on the surface of the liquid, but to the small air bubbles which are caught and held in the body of the liquid, increasing its volume. Overflow losses increase with the tendency of a liquid to retain finely divided air bubbles. The addition of antifreeze materials to water should not cause any appreciable increase in foaming and low foaming tendencies are therefore desirable in antifreeze products.
The need for keeping the foaming tendency of antifreeze solutions down to a minimum is indicated in Table IV, showing the comparative overflow losses in inhibited and uninhibited ethylene glycol on a dynamometer test of one high production engine. Although high road speeds are banned for the duration of the war, the prevalence of high engine speeds in the lower gears is still a factor affecting air entrainment and possible foaming and overflow in heavily loaded commercial vehicles.
Table IV—COMPARATIVE FOAMING DATA IN 1939 COOLING SYSTEM i
Solution Solution Antifreeze type	temper- loss after
ature 1,000 miles
Cubic centi-°F. meters
Untreated ethylene glycol._____________p_____________ 180	1,000
Improperly treated ethylene glycol________L._______ 180	4,000
Properly treated ethylene glycol___________________ 180	75
1 Dynamometer test: 60 m. p. h., solutions of freezing point 0° F.
G-7. CREEPAGE OF ANTIFREEZE SOLUTIONS
Uninhibited antifreeze materials have some tendency to loosen rust and creep through rust-filled crevices in the cooling system which previously have been plugged leaktight when using only water. Leakage-rate tests in laboratory apparatus and in vehicles have shown that this is particularly true of untreated ethylene-glycol solutions. However, in standard ethylene-glycol products containing inhibitors, the leakage rates of solutions have been found to be substantially lower than that of water.
G-8. THERMAL EXPANSION OF ANTIFREEZE SOLUTIONS
Both water and antifreeze solutions expand when heated up, making it necessary to leave an adequate air space in the radiator when the liquid is cold in order to avoid overflow losses from thermal expansion at driving temperatures. Ethanol, methanol, and ethylene-glycol antifreeze solutions all expand somewhat more than water when heated, but not nearly to the extent popularly believed. To give an idea of the relative thermal expansion rates of various antifreeze solutions as compared to water, the approximate amounts in pints expansion per gallon of liquid are shown for the temperature range of 40° to 180° F., in Table V. The cost of antifreeze, and its scarcity during the present emergency, make it imperative that expansion losses from overfilling of the radiator be avoided.
Table V.—THERMAL EXPANSION OF WATER AND ANTIFREEZE SOLUTIONS
[Pints expansion per gallon of liquid between 40° and 180° F. Water, 0.24 pint per gallon]
Solutions protecting to— Type of antifreeze	-----------------------------
+20° F. 0° F. -20° F.
Ethyleneglycol------------------------------ ‘	0.29	0.34	0.37
Methanol.___________________________________ .26	. 37	. 44
Ethanol______________________________t______	.31	.47	,54
G-9. CHEMICAL CHARACTERISTICS OF ORGANIC ANTIFREEZE SOLUTIONS
While water itself is chemically very stable, it attacks certain cooling system metals quite vigorously under the influence of conditions of heat and aeration constantly present during cooling system operation. Therefore, the cooling liquid, whether water or water solutions of antifreeze materials, must always contain a corrosion preventive if metal attack and rust formation are to be avoided. Inhibitors contained in standard organic antifreeze products greatly reduce the attack of water on metals and also stabilize the antifreeze materials
25
chemically so that effective corrosion prevention can be maintained in a normal cooling system for at least one antifreeze season.
The necessity for using corrosion inhibitors in the organic antifreeze materials is shown in Table VI, showing the comparative corrosion weight losses of various cooling system metals in inhibited and uninhibited organic antifreeze solutions and in water, as determined by a laboratory corrosion test. With inhibited liquids, the reduction in the corrosion of iron is particularly outstanding and the indicated protection to aluminum, copper, brass, and solder strongly recommends the use of summer rust preventives with water as well as the use of suitably inhibited antifreeze. However, laboratory corrosion tests cannot be depended on to predict the corrosion effects in the cooling system of inorganic salt antifreezes such as calcium chloride.
Table VI.—CORROSION TESTS ON TREATED AND UNTREATED ANTIFREEZE SOLUTIONS >
Test No.	Weight losses in milligrams per 12 square inches per 200 hours at 170° F.				
	Iron	Aluminum	Copper	Brass	Solder
1. Untreated methanol				1,995	49	29	43	24
2. Commercial methanol inhibited...	1		10	2	10
3. Untreated ethanol		1,390	21	42	4	18
4. Commercial ethanol, inhibited...	0	3	23	8	23
5. Untreated ethylene glycol		793	45	101	101	267
6. Inhibited ethylene glycol		0	0	1	1	40
7. Distilled water		1,524	5	93	93	234
8. Inhibited water		0	4	32	20	32
1 All solutions except No. 7 and 8 of freezing point 0° F.
G-10. SUGGESTIONS FOR INSTALLATION, TESTING AND SERVICING OF ANTIFREEZE
1.	Inspect the cooling system and perform any necessary services to insure that it is clean, leaktight and in proper working order.
2.	Completely drain the system by opening all drain cocks or plugs on both engine and radiator. Use a cleaning solution, if necessary, or at least flush thoroughly with water.
3.	Determine the quantity of antifreeze to use from the vehicle’s factory cooling system capacity chart and the antifreeze manufacturer’s protection table for the lowest temperature likely to be encountered.
4.	Pour the required amount of antifreeze into the radiator and finish filling with water to the proper level which will allow room for thermal expansion without overflow.
5.	Run the engine until it reaches driving temperature, covering the radiator if necessary in order to open the thermostat and establish complete circulation through the system before driving the car or exposing it to freezing temperatures. This is
necessary:
a.	To completely mix the water and antifreeze and prevent a slush ice freeze-up. (See fig. 33.)
Figure 33.—Slush freeze-up in radiator and overheating from unmixed solution.
b.	To remove any trapped air in the engine, after which it may be necessary to add more water. (See fig. 34.)
Figure 34.—Showing how air is trapped in engine by closed thermostat.
6.	Inspect the solution and test for freezing protection at least once a week. Always make the test before adding antifreeze, or water and with the solution warm. Carefully follow the instructions furnished with the tester.
7.	Replace leakage and overflow losses of solution with a mixture of water and antifreeze to give the same strength as the original filling.
8.	In case of insufficient protection or diluted solution, use the table or chart supplied by the antifreeze manufacturer to calculate the amount of additional antifreeze needed.
9.	Antifreeze Testers:
a.	Simple hydrometers without a thermometer or temperature correction chart can only be accurate for one solution temperature, usually 60° F.
26
b.	Commercial testers which will accurately read freezing protection at any solution temperature within the thermometer scale (usually 60° to 160°) are recommended.
c.	Testers designed for any one type of antifreeze (ethanol, methanol, or ethylene glycol) cannot be used for the other types.
d.	Recommended tester requirements for minimum testing accuracy are: (1) all-glass float with scale at least 2 inches long and not less than 13 divisions covering the range of commonly used concentrations; (2) range of thermometer scale 60° to 160° F., with not greater than 10 degrees temperature divisions; (3) correction chart with same number of divisions as float and thermometer scales.
e.	To check the accuracy of an antifreeze tester, use a solution of known freezing protection. For instance, a solution of one-third ethylene-glycol antifreeze and two-thirds water gives zero protection, and a half-and-half solution protects to —34° F. Check the tester accuracy with solution at different temperatures within the range of the thermometer scale.
<3-11. CONSERVATION OF USED ANTIFREEZE SOLUTIONS
To be assured of an adequate supply of antifreeze for next winter, civilian motorists should conserve the past season’s antifreeze solution. This is advisable because increased war demands for antifreeze chemicals make uncertain an adequate supply for future civilian use.
In normal times the ideal procedure is to install a fresh filling of inhibited antifreeze, but for the duration of the war it is essential to save such critical materials wherever possible. On the other hand, it is just as important to prolong the life of cooling system parts also containing critical materials and for this reason the continued use of antifreeze solution that may be corrosive should be avoided.
Corrosion inhibitors in antifreeze may be weakened and exhausted by extended or hard use. Such variables as driving mileage and speed and the condition of the engine and cooling system are important factors in the noncorrosive service life of solutions. Contaminated antifreeze solutions with exhausted inhibitors may cause more corrosion and rust formation than untreated water if their use is continued indefinitely.
The following procedure is suggested to reduce the hazards of corrosion, rust-clogging, overheating and freeze-up to a minimum, in the absence of any special recommendations from the antifreeze or vehicle manufacturer.
1.	Determine if the antifreeze solution is one of the recommended types, alcohol or ethylene-glycol. If the antifreeze is found to be a deleterious salt or oil type, it should be drained and discarded immediately and the cooling system should be thoroughly cleaned and flushed.
2.	Check the solution with a suitable antifreeze tester and record the temperature to which it is protected. Very weak solutions may not be worth saving.
3.	Preserve the antifreeze solution in a satisfactory manner. This may be done by draining the solution and storing it in clean, labeled and sealed containers, preferably glass or earthenware. If the solution is the ethylene-glycol type it may be desirable to leave it in the cooling system to avoid the possibility of drainage losses. At the present time, this practice is made possible by low car mileage as controlled by gasoline rationing and by limited driving speeds. Either of the following tests may be used to determine if solutions are suitable for further use:
a.	Dip blue litmus paper in the antifreeze solution. If it does not turn a distinct pink or red, it is suitable for further use.
b.	Allow a sample of the solution to stand overnight in a clear glass container. If the solution is suitable for further use, it will clear up practically water-white or with at least a trace of the color of the original solution.
If the blue litmus paper turns a distinct pink or red when dipped in the antifreeze solution or if the solution upon standing does not finally clear up, it should be discarded.
4.	Before stored solution is returned to the cooling system in the fall, it should be tested again for antifreeze strength. If necessary to increase the freezing protection, fresh material, preferably of the same brand, should be added.
5.	When antifreeze of the ethylene-glycol type is used for more than one winter, it should receive more than normal inspection and test. A special reinhibitor made and recommended by the manufacturer of the antifreeze in use in the car should be used. Other inhibitors, regardless of their suitability or lack of suitability for other purposes, must not be used for this purpose.
6.	The mixing of different brands of antifreeze in the cooling system should be limited to those having the same basic materials, such as ethylene-glycol or alcohol. Mixtures of ethylene-glycol and alcohol cannot be correctly tested with a commercial antifreeze tester.
Attention should be called to the further necessity of following the car manufacturer’s normal recommendation for the cleaning, preservation, and proper care of the cooling system.