Lesson 5/Learning Event 2
Usually, a cooling system works by moving a liquid over the hot cylinder and combustion chamber walls. The
liquid absorbs heat and carries it away. This is a liquid-cooling system.
Sometimes a cooling system uses no liquid. Instead, air is moved over the hot walls of the cylinders and
combustion chambers to carry away heat. This is an air-cooling system.
SOME HEAT IS NEEDED
At the same time, the engine must not be allowed to run too cold either. An engine running too cold does not
burn all the fuel taken into the combustion chambers and will cause a lot of sludge to form in the crankcase.
This causes poor gasoline mileage, forms carbon deposits, increases wear, and cuts down on engine power.
JOBS OF THE COOLING SYSTEM
The cooling system does three jobs to provide a satisfactory temperature operating range for the engine. First,
it removes the unwanted heat. Second, it regulates the engine temperature to keep it just right during all
operating conditions. Last, when the engine is first started, it makes the engine warm up to its normal
operating temperature as soon as possible.
METHODS OF COOLING
Fuel, Oil, and Exhaust
Although they are not ordinarily thought of as being a part of the cooling system, the fuel, lubrication, and
exhaust systems help a lot toward cooling the engine. The repairer must not overlook these systems as trouble
here may appear to be problems in the cooling system.
Fuel. When fuel enters the engine, it is cool; therefore, it absorbs or soaks up a lot of the heat. You can get
an idea of just how cool the fuel is when it enters the engine by feeling the carburetor throttle body on an
engine that is running. The throttle body will feel cool, even though the engine is hot.
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