Description:
Below is an explanation of this system's operation
The Cooling System
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.
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.
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.
On the other hand, if an engine runs at too low a
temperature, it is inefficient, the oil gets dirty (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.
There are two types of cooling systems; liquid cooling
and air cooling. Most auto engines are cooled by the liquid type; air
cooling is used more frequently for airplanes, motorcycles and
lawnmowers.
Liquid cooled engines have passages for the liquid, or
coolant, through the cylinder block and head. The coolant has to have
indirect contact with such engine parts as the combustion chamber, the
cylinder walls, and the valve seats and guides. Running through the
passages in the engine heats the coolant (it absorbs the heat from the
engine parts), and going through the radiator cools it. After getting
"cool" again in the radiator, the coolant comes back through the engine.
This business continues as long as the engine is running, with the coolant
absorbing and removing the engine's heat, and the radiator cooling the
coolant.
A cooling system pressure tester is used to check the
pressure in the cooling system, which allows the mechanic to determine if
the system has any slow leaks. The leak can then be found and fixed before
it causes a major problem.
The Heater Core
The heater core is a smaller version of the radiator that
is used to keep your toes warm when it's cold outside.
The heater core is mounted under the dash board. Some of
the hot coolant is routed through this little radiator, by more hoses. A
small electric fan is also mounted there especially for the purpose of
directing the heat inside the car. To turn this fan on, you use a switch
called "fan" or "blower," located on your control panel. The principle is
exactly the same as the one used in the radiator for your engine, except
that the heat is released inside the car instead of outside. Most engines
use the heater core to warm the air coming from the air conditioner if the
dash setting is not on "cold". More efficient designs don't do this
because it makes the engine work harder than it has to. They cycle the
compressor on and off to lessen the cooling output.
If your car is running hot, turning the heater on will
help to reduce the heat in the engine. Unfortunately, most cars don't
overheat in the winter. |
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