COOLING SYSTEM - TM-9-2320-270-20-10034

TM 9-2320-270-20-1

COOLING SYSTEM

Coolant is drawn from the bottom of the radiator by the water pump. The coolant passes through the

water pump and is forced into the heat exchanger. As the coolant goes through the heat exchanger it

cools down the transmission fluid. From the heat exchanger, the coolant goes through the oil cooler to

cool the engine oil. From the oil cooler, the coolant goes through the engine cylinder block to help

cool the engine. The coolant leaves the engine through the cylinder heads and goes into the thermo-

stats. If the coolant temperature is below normal operating temperature, the coolant is drawn back

into the water pump where it is sent back through the heat exchanger, oil cooler, and engine. (A small

amount of coolant leaves the right thermostat and goes into the top of the radiator where air bubbles

are removed before it is sent to the water pump). As the coolant temperature gets near the normal

operating temperature, the thermostat valves start to open. Some of the coolant is drawn through the

radiator where it is cooled down before it goes to the water pump. When the coolant temperature

reaches the normal operating temperature, all of the coolant is drawn through the radiator to be

cooled down before it goes to the water pump. The fan draws air through the radiator to help cool down

the coolant.

Water Pump The centrifugal-type water pump is mounted on the front of the engine and is driven by

the front camshaft gear. The water pump has an impeller with blades that forces the coolant outward

as it rotates. The water pump shaft seal (used to seal the impeller shaft from leaking) is the only

moving water joint in the cooling system.

Heat Exchanger - In the heat exchanger, transmission fluid circulates through tubing. As coolant

passes through the heat exchanger, it absorbs the heat of the transmission fluid through the tubing.

Oil Cooler The oil cooler has 24 plates used to absorb the heat of the engine oil. Coolant passing

through the oil cooler helps to cool down the plates.

Engine The engine contains a water jacket. In the cylinder block, the water jacket surrounds the

cylinders completely. In the cylinder head, the water jacket covers the combustion chambers at the

top of the cylinders. As coolant passes through the water jacket, it absorbs the heat made by the

engine.

Thermostats The two semiblocking bellows type thermostats are mounted to the water outlet ends of

each cylinder head. The thermostats contain a liquid which boils at a certain temperature. When that

temperature is reached, the boiling liquid creates gas pressure which opens the thermostat valve.

When the liquid cools, gas pressure is reduced and the valve closes.

Radiator The radiator is made up of a top tank, a radiator core, and a bottom tank. The top tank

collects incoming coolant and spreads it across the top of the radiator core. An overflow pipe on the

top tank provides an opening for the escape of coolant or steam that might cause too much pressure in

the cooling system. A radiator cap is also located on the top tank. The cap has a pressure valve and a

vacuum valve which open and close to help keep the cooling system at the proper operating

temperature. The core is made up of many small tubes and air fins. As coolant passes through the

radiator, heat is transferred to the tubes and fins, and carried away by the air moving through the

core. The bottom tank collects the coolant from the core and sends it to the water pump through the

radiator outlet.

Fan - The fan pulls large amounts of air through the radiator core. The air is used to remove heat from

the radiator, and also to help cool down the outside of the engine.

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