INTRODUCTION TO THE HMMWV - OD1615 - LESSON 1/TASK 2
The air then continues to travel through the air to manifold duct and the
system because of the high temperatures they generate during operation.
High temperatures are necessary to generate the high gas pressures that act
on the head of the piston.
Power cannot be produced efficiently without
However, it is not possible to use all the heat of
combustion without harmful results.
The temperature in the combustion
chamber during the burning of fuel is well above the melting point of iron.
Therefore, if nothing is done to cool the engine during operation, valves
will burn and warp, lubricating oil will break down, and bearings and
pistons will overheat, resulting in engine seizure.
The engine cooling system is a pressure type cooling system with
thermostatic control of coolant circulation. The cooling system dissipates
the heat generated from combustion and maintains the engine operating
temperature at the most efficient range.
radiator, surge tank, thermostat, 10 blade fan and drive clutch, water pump,
radiator hoses, pulleys and drive belts, and the radiator shroud.
When the engine is cold, and the thermostat is closed, coolant is circulated
As the engine coolant reaches 190 F,
through the water pump and engine.
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 to 230 F.