Figure 4-23. Cylinder Block Drain Location

d. Check radiator

water pump gasket

surfaces and hose connections for leakage.

e . Blow out debris and foreign material from

radiator core by directing a compressed air stream

through the radiator from outside the engine

compartment.

413. COOLING SYSTEM DRAIN AND REFILL.

a. Dram all coolant from engine cylinder block

and radiator. (See figure 4-23 for cylinder block

drain location.)

Note

Figure 4-23. Cylinder Block Drain Location

Draining of cooling system is most effective

when the engine has just been operating, as

the combination of heat and circulation of

cause sudden boiling of the coolant and a

the water will hold some of the sediment in

dangerous steam flash. Always loosen the

suspension, to be drained off with the

cap slowly and allow the pressure to vent

coolant. Disconnecting the lower radiator

off slowly before removing cap.

hose will allow larger particles of sediment

and scale to be drained off.

a. Remove radiator cap slowly, and check

coolant level. The coolant level should be checked

b. Close cylinder block and radiator drains and

with the engine shut off.

refill cooling system, adding cleaning compound,

Military Specification MIL-C-10597.

b. Make certain coolant level reaches the coolant

level tap inside the filler neck, 2-3/4 inches below

c. Operate engine for approximately 15 minutes,

the top of the filler as shown in figure 4-22, but

then completely drain the system and flush with

never higher.

clean water.

d. Refill cooling system with clean water or

anti-freeze solution, to the level shown in figure

4-22.

Never pour cold water or cold anti-freeze

solution into the radiator of an overheated

e. Operate engine and check for leaks at radiator,

engine. Allow the engine to cool and avoid

water pump gasket surfaces, and hose connections.

the danger of cracking the cylinder head or

Recheck coolant level as engine will expel trapped

block. Keep the engine running while

air while operating.

a d d i n g water or anti-freeze. When using

ethylene-glycol

(permanent-type)

f. Check radiator cap gasket surfaces, and replace

a n t i - f r e e z e , the solution must contain a

cap if sealing surface appears cracked, broken or

minimum of 40% water.

deteriorated. See figure 4-24.

c. Use only clean water, or clean water and

g. Inspect pressure cap for freedom of operation.

anti-freeze solution, in refilling the radiator. Add 1

Pressure caps employ a spring loaded, rubber-faced

ounce per gallon of soluble oil to the coolant. If

valve which presses against a seat in the radiator

the truck is likely to be exposed to temperatures

top tank. Pressure caps employ either a vacuum

lower than 32F, check anti-freeze protection level

valve held against its seat under spring pressure, or

using a hydrometer.

4-17