Lubrication System.

Troubleshoot The High Mobility Multi- Purpose Wheeled Vehicle (HMMWV)
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shroud.

When the engine is cold, and the thermostat is closed, the coolant is

recirculated through the water pump and engine.

As the engine

coolant reaches 190 F, the thermostat opens allowing coolant to flow

through the radiator before returning to the water pump and the

engine. Any air or vapor in the cooling system will be forced to the

surge tank under the liquid level and leave through the vent tube.

As the system cools, the extra coolant in the tank will be drawn back

to the radiator. The normal operating temperature is between 190 F

to 250 F.

The radiator is mounted at an angle of approximately 45 to

accommodate the low silhouette of the vehicle.

The radiator holds

four gallons of coolant, while the surge tank holds half a gallon.

The radiator shroud channels the air flow between the radiator and

fan for more efficient operation.

The fan is mounted on the fan

drive clutch that activates the fan when the coolant temperature

reaches approximately 220 F. Normally, a 50-50 mixture of water and

ethylene glycol base antifreeze should be used in the cooling system.

This is to prevent freezing and to protect the metal components.

A separate oil cooler is mounted in front of the radiator.

This

cooler is divided into two parts. The top half is for transmission

and transfer case oil, and the bottom half is for engine oil.

(2) When the cooling system pressure reaches approximately 15 psi,

a valve in the surge tank cap opens and lets excess pressure escape

into the atmosphere. Another valve opens at approximately two inches

of mercury (vacuum) and allows air back into the cooling system.

Lubrication System.

(1) Purpose of the Lubrication System. The lubrication system in

an automotive engine provides a constant supply of oil to all moving

parts; this fresh oil is important to minimize wear, flush bearing

surfaces, and remove the localized heat