The
purpose of the engine's cooling system is to remove excess heat from the
engine, to keep the engine operating at its most efficient temperature,
and to get the engine up to the correct temperature as soon as possible
after starting. Ideally, the cooling system keeps the engine running at
its most efficient temperature no matter what the operating conditions
are.
| As fuel is burned in the
engine, about one-third of the energy in the fuel is converted into power.
Another third goes out the exhaust pipe unused, and the remaining third
becomes heat energy. |
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A cooling system of some
kind is necessary in any internal combustion engine. If no cooling system
were provided, parts would melt from the heat of the burning fuel, and the
pistons would expand so much they could not move in the cylinders (called
"seize"). |
The cooling system of a
water-cooled engine consists of: the engine's water jacket, a thermostat,
a water pump, a radiator and radiator cap, a cooling fan (electric or
belt-driven), hoses, the heater core, and usually an expansion (overflow)
tank.
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Fuel burning engines
produce enormous amounts of heat; temperatures can reach up to 4,000
degrees F when the air-fuel mixture burns. However, normal operating
temperature is about 2,000 degrees F. The cooling system removes about
one-third of the heat produced in the combustion chamber.
The exhaust system takes
away much of the heat, but parts of the engine, such as the cylinder
walls, pistons, and cylinder head, absorb large amounts of the heat. If a
part of the engine gets too hot, the oil film fails to protect it. This
lack of lubrication can ruin the engine.
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On the other hand, if an
engine runs at too low a temperature, it is inefficient, the oil gets
viscous (adding wear and subtracting horsepower), deposits form, and fuel
mileage is poor-- not to mention exhaust emissions! For these reasons, the
cooling system is designed to stay out of the action until the engine is
warmed up. |
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