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 above
information is directly from the Auto Insight program which you
can buy online from AutoEducation.com. Common Problems: Let's
look at the common problems cars have with the cooling system.