Section X. MAINTENANCE OF COOLING SYSTEM

(fed. spec. P-D-680). Pump clean solvent through the

(4) Inspect the primer tubes for damaged

pump to thoroughly flush the interior.

threads on tube nuts, kinked tubing, cracked tubing

(2) Clean all lines and fittings with cleaning

ends, or other damage. Replace damaged tubes.

solvent (fed. spec. P-D-680). Blow out all lines with

(5) Inspect all fittings for cracks, damaged

compressed air to make sure they are not clogged.

threads, and other damage; replace damaged parts.

(3) Check the exterior of the primer pump for

c. Installation. Install the primer pump, lines, and

cracks or obvious damage. Operate the pump handle.

fittings as shown in figure 4-14. After installation,

Make sure it operates freely without binding. Replace a

operate the primer pump and check all connections for

damaged priming pump.

leaks. Correct any leaks.

Section X. MAINTENANCE OF COOLING SYSTEM

4-27. Description

b. Disconnect the hoses connecting the engine and

radiator. With the radiator cap closed tightly, use a

a. The engine cooling system is a conventional

flushing gun as shown in figure 4-15 to reverse-flush the

automotive type in which coolant is circulated through

radiator. Fill the radiator with water, then blow it out with

the cylinder block to remove the heat of combustion

compressed air, applying pressure slowly to prevent

from the operating parts of the engine. The coolant is

radiator damage.

Repeat several times until the

then passed through the radiator, which acts as a large

expelled flushing stream is clear.

heat exchanger to dissipate the heat to the atmosphere.

The water pump maintains the flow of coolant through

c. Remove the thermostat (para 4-29) from the

the engine.

engine and use a flushing gun as shown in figure 4-16.

Fill the cylinder block with water before applying air

b. A thermostat is installed in the engine to prevent

pressure. When the block is filled, expel the water with

the flow of coolant into the radiator when the engine is

an 80 psi air stream. Repeat until the expelled flushing

cold. Instead, the coolant is bypassed directly to the

stream is clear.

water pump and recirculated into the block without being

cooled in the radiator. In this way, the engine heats

more rapidly, providing efficient operation more quickly.

When the coolant in the cylinder block reaches

operating temperature, the thermostat opens and the

coolant is forced to flow through the radiator.

c. To assure efficient operation of the cooling

system, it is important to keep the exterior of the

radiator clean and free from bugs, dirt, and debris. It is

also necessary to keep the interior of the radiator and

the engine block flushed out to prevent accumulations of

rust and scale which can prevent proper heat transfer.

4-28. Cleaning and Flushing the Cooling System

a. Clean the exterior of the radiator by flushing a

stream of water through it in a direction opposite that of

the cooling fan flow. Since this engine uses a pusher

type fan, it is necessary to squirt the water from the

outside of the radiator inward toward the engine. Cover

the engine with a piece of plastic film to prevent

saturating the components before attempting to flush out

the exterior of the radiator.

Figure 4-15. Reverse-flushing the radiator.

4-19