ENGINE OVERHEATS

TM 5-4320-234-12

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

ENGINE--Continued

b. Wipe the exterior of the spark plugs with a cloth dampened with dry cleaning solvent (fed. spec PD-680),

dry thoroughly.

c. Check the ceramic insulator for cracks, porosity, and other damage.

d. If the electrodes of the spark plugs are not too badly burned, remove the scale and other deposits from

them. This can be done by a sand-blast-type cleaner or with a contact file.

e. Inspect the electrodes for severe burning, cracks, and other damage. Replace any spark plug whose

condition is doubtful.

f. Make sure all spark plugs are gapped to 0.025 inch before installation. Install and torque the spark plugs to

35 foot pounds.

5. ENGINE OVERHEATS

Step 1. Check oil level.

If oil level is low, fill to the proper level with recommended oil.

Step 2. Check that radiator stone shield is open and that radiator is clear of foreign matter.

Always open stone shield before operating engine. Remove foreign matter from radiator.

Step 3. Check for low coolant level.

Refill with approved coolant as required.

Step 4. Check for loose or damaged fan belt.

a. Inspect the fan belt for cracks, brittleness, and severe glazing. Replace a damaged fan belt.

b. Loosen the adjusting screw on the alternator adjusting strap and push the alternator toward the engine to

loosen fan belt tension. Slip the fan belt off the alternator drive pulley and remove it from the fan and drive

pulley.

c. Position a new fan belt on the fan and drive pulley and alternator drive pulley.

d. Pull the alternator away from the engine with hand pressure to tighten the fan belt.

e. Hold the alternator away from the engine and tighten the adjusting screw. The fan belt should be tensioned

so that it can be deflected approximately 3/4 inch with thumb pressure at a point midway between pulleys at

the longest belt span.

Step 5. Check for a clogged radiator.

a. Cover the engine with a piece of plastic film to prevent saturating the components before attempting to flush

the exterior of the radiator.

b. Clean the exterior of the radiator by flushing a steam of water through it in a direction opposite that of the

cooling fan. 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.

c. Disconnect the hoses connecting the engine and radiator. With the radiator cap closed tightly, use a

flushing gun to reverse-flush the radiator. Fill the radiator with water, then blow out the water with compressed

air, applying pressure slowly to prevent radiator damage. Repeat several times until the expelled flushing

stream is clear.

Step 6. Check for a defective water pump.

a. Loosen the adjusting screw on the alternator adjusting the strap and push the alternator toward the engine

to loosen fan belt tension.

b. Check the rotation of the water pump shaft by turning the fan by hand. It must turn easily without catching

or binding. Replace a leaking or damaged water pump.

c. Remove the fan belt from the fan and drive pulley. Remove the four capscrews that secure the fan to the

water pump pulley; remove the fan.

d. Drain the coolant from the radiator and cylinder block. Disconnect coolant hoses and bypass tube from the

water pump. Remove the elbow and adapter. Remove three capscrews and lockwashers that secure the water

pump to the cylinder block; remove the water pump and gasket.

e. Position water pump and gasket on the cylinder block and secure with screws and lockwashers.

Install the elbow and adapter. Connect coolant hoses and bypass tube to the water pump. Add coolant to the

radiator and cylinder block.

f. Install the fan on the water pump pulley and secure with capscrews. Install fan belt on the fan and drive

pulley and alternator drive pulley.

g. Pull the alternator away from the engine with hand pressure to tighten the fan belt.

h. Hold the alternator away from the engine and tighten the adjusting screw. The fan belt should be tensioned

so that it can be deflected approximately 3/ inch with thumb pressure at a point midway between pulleys at the

longest belt span.

Step 7. Check for a defective thermostat.

a. Drain coolant from the radiator. Remove radiator top hose and water pump bypass tube.

b. Remove two nuts and lockwashers and remove water outlet elbow, gasket, and thermostat.

c. Inspect the thermostat for obvious defects, including ruptured bellows and distortion. If the valve, when

cold, can be pushed off its seat with only slight effort, the thermostat is defective and must be replaced.

d. Check the thermostat operation as follows:

(1)

Hang the thermostat by its frame in a container of water so that it does not touch the container.

Hang a thermometer in the container to maintain a check of water temperature.

(2)

Heat the water slowly while watching the thermometer and thermostat. The thermostat must start

to open before the thermometer indicates 180 F. (82.22 C.). Replace the thermostat if it fails to open at

180 F (82.22 C) or if it starts to open before 160 F. (71.11 C).

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