CHAPTER 5 REPAIR OF COOLING SYSTEM

TM 10-3930-633-34

CHAPTER 5

R E P A I R OF COOLING SYSTEM

the adapter fitting and pressurize the cooling

5-1. General

system until bubbles are observed in the water

The cooling system is of the pressurized type

container. Discontinue pumping when bubbles

and utilizes a tube and fin type radiator. The

appear.

coolant is drawn from the bottom of the radiator

( 7 ) When the bubbles cease, read the

by the water pump, which circulates the coolant

pressure gage. The gage reading is the pressure

through the engine block. As the coolant enters

relief of the cap a n d s h o u l d b e w i t h i n

the block, it travels through cored passages to

specifications. If the pressure reading exceeds the

cool the entire length of each cylinder wall. Upon

specified limit, replace the radiator cap.

reaching the rear of the cylinder block, the coolant

(8) If bubbles continue and the pressure

is directed upward into the cylinder head where it

drops below 10 PSI, the radiator cap is not

cools the combustion chambers, valves and valve

holding pressure. Release pressure and wash cap

seats on its return to the front of the engine.

in clean water to dislodge any foreign matter from

5-2. Cooling System Test

the valves. Check the rubber sealing surface of

a. General. The cooling system test as

the cap and also the cap sealing surface in the

outlined in the following paragraph will reveal

radiator neck. Inspect the cam lock flanges on

such problems as blown gaskets, internal or

both sides of the filler neck for maximum cap

external system leakage, or pressure cap

engagement.

malfunction. The type of pressure tester used

(9) Recheck the cooling system as outlined in

should be fitted with a gage, and be adaptable to

steps 6 and 7. If the cap still does not hold

a hose connection.

pressure, t h e cap is damaged and must be

b. Procedure.

replaced. Recheck system after a new cap is in-

(1) Shut off the engine. To prevent loss of

stalled to assure that the system will now hold

coolant and to avoid the danger of being burned,

pressure.

place a cloth over the cap and rotate the cap

(10) If the bubbles in the water container

slowly counterclockwise to first stop and allow

c e a s e and radiator cap is within pressure

pressure to escape completely. Then turn cap

specifications, observe gage reading for ap-

again slowly counterclockwise to remove.

proximately two minutes. Pressure should not

(2) After the cooling system pressure has

drop during this time.

been released, remove the radiator cap, wet the

(11) If pressure drops, check for leaks at the

rubber sealing surface and reinstall cap tightly on

engine to heater core hoses, engine to radiator

the radiator.

hoses, by-pass hose, water valve hose (A/C

(3) Disconnect the electrical connector from

equipped), thermostat housing gasket, etc. Any

the engine temperature sending unit and remove

leaks which are found must be corrected and the

the temperature sending unit from the manifold.

system rechecked.

With the radiator cap installed, only a small

(12) If the system holds pressure, remove

amount of coolant will be lost when the sending

the radiator cap to release the pressure, then

unit is removed.

reinstall the cap.

(4) Install an adapter fitting (3/8 N. P. T.

(13) Remove the adapter from the manifold

male thread on one end, and a hose connection on

or cylinder head and reinstall the temperature

the other end to accommodate the tester hose)

sending unit. Check coolant level and replenish if

tightly into the intake manifold or cylinder head

necessary with the correct coolant solution.

in place of the sending unit.

5-3. Radiator

(5) Remove the radiator overflow hose from

a. Maintenance. Maintenance of the radiator

the retainer clips. Make sure the hose is firmly

consists of keeping the exterior of the radiator

installed on the radiator overflow tube and is in

core clean, the interior free from rust and scale,

good condition. Insert the free end of the overflow

and the radiator free from leaks. Check the

hose into a container of water.

cooling system fluid level and for leaks at each

(6) Attach the pressure pump and gage to

5-1