Section IV. COOLANT

Malfunction

Probable causes

Corrective action

c. Rupture of radiator tube

c. Repair, splice, or replace radiator tube (s)

4. Loss of coolant (continued)

(para 3-32)

d. Unsoldered joints, cracked or worn

d. Solder (epoxy) aluminum radiators or patch

spots or fittings

defective areas (para 3-43)

e. Open drain cock

e. Close drain cock

a. Air in coolant

a. Keep coolant level above radiator tubes

5. Corrosion

(para 2-20)

b. Impurities In coolant

b. Change coolant frequently (para 2-19)

c. Contamination of coolant

c. Drain and clean radiator Add fresh coolant.

Check coolant frequently for cleanliness

(para 2-19)

a. Combustion gas leakage into the

a. Drain coolant Add water then run engine. If

6. Foaming of coolant

coolant

foaming continues, conduct combustion gas

(para 3-21) and air suction test (para 3-19).

b. Air suction into the cooling system

b. See a above

Section IV. COOLANT

percent antifreeze solution when heated from -20 to

2-25.

Importance of Radiator Coolant

180F is nearly pint per gallon. If a 5-gallon cooling

Line an endless belt conveyor, the flow of coolant is

system containing a 50 percent solution where filled

continually carrying a load of heat from the engine

completely full with the coolant temperature at -20, about

waterjacket into the radiator During operation, transfer of

212 pints of solution would overflow out of the radiator by

waste heat from inside engine to outside air through

the time the coolant temperature had reached 180F.

coolant must never be interrupted. Coolant plays as

important a part in the operation of the automotive engine

2-28.

Boiling and Evaporation

as fuel or lubricating oil.

a. Nature of Boiling Boiling causes coolant to

2-26.

Water as a Coolant

change rapidly and violently from a liquid to a gas. Boiling

of a liquid is controlled by two conditions, temperature of

Water has always been the most commonly used coolant

liquid and pressure upon it. Boiling of water takes place at

for internal combustion engines because it has good ability

212 F under pressure of the atmosphere at sea level.

to transfer heat and can be readily obtained almost

When water boils and changes to a gas called steam, it is

anywhere. Some properties of water, such as its boiling

capable of expanding 1,600 times. Therefore, a gallon of

point and freezing point, limits its usefulness as a coolant.

water can make as much as 1,600 gallons of steam.

The natural corrosive action of water on metals is definitely

However, when water boils in the limited space of an

undesirable.

engine water jacket, this extreme expansion cannot take

place. Under this condition, the force of the expansion

2-27.

Thermal Expansion

creates steam pressure.

b. Effect of Altitude (fig. 2-22). Air pressure on

Antifreeze compound solutions expand slightly more than

each at sea level is about 15 pounds per square inch.

water when heated. When the temperature of a 50

This pressure becomes less at higher altitudes, and the

percent antifreeze solution is raised from 40 to 180F, the

reduced pressure causes water and other liquids to boil at

solution expands about 1/7 pint per gallon more than water

a lower temperature. For example, the reduced air

under the same conditions. However, during very cold

pressure at 1,000 feet above sea level lowers the boiling

weather, the range between atmospheric and maximum

point of water from 212 to 210F. At an altitude of 5,000

operating temperatures is much greater than when water

feet, the boiling point of water is only 203 F.

is used, and thermal expansion of solution is therefore a

more serious matter. For example, the expansion of a 50

2-20