Section XII. MAINTENANCE OF COOLING SYSTEM

TM 10-3930-633-12

Section XII. MAINTENANCE OF COOLING SYSTEM

4-63. General

The thermostat is a heat-operated valved. It

should always be maintained in working order

a. The cooling system is of the pressurized

and the vehicle should never be driven without

type and utilizes a tube and fin type radiator. The

one installed, as there would then be no control of

coolant is drawn from the bottom of the radiator

engine temperature. The temperature at which

by the water pump, which circulates the coolant

the thermostat opens is preset and cannot be

through the engine block. As the coolant enters

altered.

the block, it travels through cored passages to

d. Thermostat Test and Replacement. When

cool the entire length of each cylinder wall. Upon

the thermostat is not operating properly, the

reaching the rear of the cylinder block, the coolant

engine may run too hot or too cold. Overheating

is directed upward into the cylinder head where it

may damage the thermostat so that its valve will

cools the combustion chambers, valves and valve

not function properly, and a cold engine will not

seats on its return to the front of the engine.

achieve full efficiency. Rust can also interfere

b. At the front of the engine, the coolant flows

with thermostat operation. To test the ther-

into the coolant outlet connection, past the

mostat, place it in water heated approximately

thermostat if it is open, and into the top radiator

250 F. (17 C.) above the temperature stamped on

header tank. If the thermostat is closed, a small

the thermostat valve. Submerge the bellows

portion of the coolant is returned to the water

completely and agitate the water thoroughly. The

pump for recirculation. The entire system is

valve should open fully. Next, place the ther-

pressurized at 12-15 PSI.

mostat in water heated approximately 100 F. (11 0

4-64. Hoses and Thermostat

C.) below the temperature stamped on the

a. Inspection of Hoses. Air, heat, and water

thermostat valve. Submerge the bellows com-

deteriorate radiator hoses in two ways: by hard-

pletely and agitate the water thoroughly. The

ening or cracking which destroys flexibility and

valve should close completely. If the thermostat

causes leaks; by softening and swelling which

fails either of these tests, it should be replaced

produces lining failure and hose rupture and

with a new one of the same type and rating.

clogging. Examine hoses spring and fall for

KEY to fig. 4-33:

possible need of replacement or tightening. If

1. Clamp

hoses are collapsed, cracked, or indicate a soft

2. Upper hose

condition on the inside, they should be replaced.

3. Screw

b. Replacement of Hoses. Refer to figure 4-33

4. Water outlet elbow

5. Clamp

for parts relationship of cooling system parts.

6. Cap

When installing a new hose, clean the pipe

7. Gasket

connections and apply a thin layer of nonhard -

8. Thermostat

ening sealing compound. Hose clamps should be

9. V-belt set

10. Clamp

properly located over the connections to provide

11. Lower hose

secure fastening. The pressurized cooling system

12. Drain cock

pressure can blow off improperly installed hoses.

13. Radiator cap

c. Thermostat. The cooling system of the

14. Screw

15. Nut

engine is designed to provide adequate cooling

16. Rubber mount

under most adverse conditions. However, it is

17. Washer

necessary to employ some device to provide quick

18. Washer

warming and to prevent overcooking during

19. Washer

normal operation. Automatic control of engine

20. Band strap

21. Radiator

operating temperature is provided by a water flow

control thermostat installed in the water outlet.

4-50