COOLING SYSTEM

TM 9-2320-391-10

M1078A1 SERIES THEORY OF OPERATION -

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Continued

COOLING SYSTEM

The Cooling System protects the engine, transmission, and air compressor by providing a

means of removing the heat generated during operation of the vehicle.

1. The radiator pressure cap, in combination with the ethylene glycol-based antifreeze,

effectively raises the boiling point of the coolant to well above 212 F (100 C).

2. The dual thermostats help the engine to warm up quickly by remaining closed until the

coolant temperature reaches approximately 199 F (93 C). When the coolant

temperature reaches approximately 199 F (93 C), the thermostats open and coolant

is circulated through the water jacket in the engine to maintain the correct operating

temperature for the engine. Coolant is drawn from the radiator, through the

transmission oil cooler, and circulated through the cooling system by the water pump.

When the personnel heater is in use, warm coolant is used to heat the air in the cab

before being returned to the radiator. Otherwise, coolant is returned directly to the

radiator to be cooled. Heat is drawn from the radiator by the engine fan pulling air

over the radiator cooling fins.

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