Figure 4-24. Radiator Cap Sealing Surface

Figure 4-25. Pressure Testing Radiator Cap

temperatures, I f t h e t h e r m o s t a t i s s u s -

pected of being faulty, it may be tested

and/or replaced as follows:

CAUTION

Never run the engine with the thermostat

removed.

Removal of thermostat will allow

Figure 4-24. Radiator Cap Sealing Surface

water to bypass the radiator and circulate

only through the engine, causing serious

overheating and resultant engine damage.

a weighted vacuum valve which hangs open until

forced closed by a surge of vapor or coolant. Check

Drain the cooling system as outlined

to be sure components are free to operate.

in paragraph 4-13.

Note

Remove the bolts which retain the

water outlet elbow to the cylinder head

If a new cap is required, always install a cap

and thermostat housing.

of the same type and pressure rating.

NOTE

h. The radiator pressure relief valve can be tested

Mark or tag bolts during removal, so that

for proper operation by means of the cooling

they may be installed in their original

system tester shown in figure 4-25. This device is

holes at time of assembly.

manufactured by the Stant Manufacturing Co., and

comes equipped with adapters so that it can be

Remove thermostat by pulling out

used to check the radiator and the radiator cap.

from housing.

i. Inspect for dented or clogged overflow pipe. To

Hand the thermostat in a pan or

remove clogged material, run a flexible wire

glass breaker, so that no part of the

through pipe until obstruction is removed. When a

thermostat touches the bottom or sides

pressure cap opens the sudden surge of vapor or

of the container, see figure 4-17.

liquid must pass thru the overflow pipe. If the pipe

Also suspend in the water a thermometer

is dented or clogged, the pressure developed by the

of known accuracy, having a range of at

obstruction may cause damage to radiator or hoses.

least 250 F.

AND

TEST

4-14. THERMOSTAT

H e a t t h e w a t e r t o 1 5 8 F . , and

REPLACEMENT. An engine which runs too hot or

observe action of bellows in the ther-

too cold will not perform properly, will lack

mostat as water termperature is raised

p o w e r , a n d create more maintenance problems

an additional 10 F. at a time, pausing

than

engine

operating

the

proper

at 168 F., 178 F, and 188 F . f o r o n e

minute to check if thermostat is

beginning to open.

4-18