by D. O'Larde

Created on: October 08, 2008   Last Updated: October 09, 2008

To have a better chance of succeeding in the repair of a cooling system one must know how the system works and the function of each essential elements of the cooling system of an internal combustion engine. The efficiency of an internal combustion engine is from 20% to 33% because of the temperature limitations of materials used in the construction of the engine. Much of the heat energy produced by the fuel combustion has to be dissipated so that the engine pistons and cylinders will not seize and other engine parts will not melt.

Only about one third of the heat energy produced by the fuel combustion in the engine cylinders is converted to mechanical energy to move a vehicle. About one third is wasted through the exhaust system and the rest needs to be dissipated to the surrounding air. While there are air-cooled engines like the Volkswagen Beetle of old, most cars have engines where the surrounding air is not sufficient to maintain an engine temperature range for efficient operation of the engine. Water mixed with antifreeze coolant of ethylene glycol circulates from the bottom tank of the radiator to the water jacket surrounding the engine cylinders absorbing heat not dissipated to the surrounding air of the engine to the top tank of the radiator. The heat absorbed by the coolant is dissipated in the radiator which is located at the front of the engine very much exposed to the outside air but protected from mechanical damage with a screen and/or grill guard and the hood. Essentially, the cooling system consists of the following.

Engine water jacket. Around the engine cylinders is a space where the coolant is pumped into to absorb excess heat.
Thermostat. The thermostat valve is normally closed and opens when the temperature around the engine cylinders is within the range to allow the coolant to continue with its journey to the radiator.
Water pump.It pumps the coolant from the bottom tank of the radiator to the system and back.
Radiator. It is constructed with tubes and fins to form a large cooling surface area to increase or improved the heat transfer and dissipation of the heat to the atmosphere.
Radiator cap. It is rated to operate less than 14 to 17 psi to prevent the coolant from splashing out the filler opening.
Coolant reserve tank. It serves not only as a reserve tank but as an expansion chamber for the coolant should pressure exceeds the radiator cap rating.
Fan. It is designed to draw cooling air through the radiator core when vehicle is moving slowly or engine is idling and operates automatically.
Rubber hoses. The hoses serve as path for the coolant from one cooling system area to another where needed such as from the engine to the top tank of the radiator.
Basically, it is important to know that cooling deteriorates over time and the possible items to fail are the thermostat, water pump, radiator, radiator cap, fan, and rubber hoses. An indicator will show on the driver's panel when the engine is overheating and it is fair to say that one or more of the cooling system parts could be failing to function the way they should. Also, it could be time to flush the system because of excessive rust and lime on the walls of the engine water jacket and heat transfer from walls to coolant is impaired.

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