Cooling system components
The primary components in a vehicle cooling system are:
The radiator is located in a convenient position under the hood of the vehicle. Its actual location under the hood depends on the engine configuration, available space and the shape or line of the hood itself.
The radiator consists of top and bottom tanks, and a core.
The radiator core allows the coolant to pass through it in either a vertical down or horizontal cross flow direction. In addition, the radiator core serves as a good conductor of heat away from the engine.
The header tank, or reservoir, can be mounted separately from the radiator. It has a supply of coolant and is located higher than the top of the radiator. The reservoirs are usually made of hardened plastic, which allows for a visual checking of the fluid level through the plastic.
On some tanks, a pressurized radiator cap may have been fitted.
The pressurized radiator cap is used to increase the boiling point of the coolant. It can be located directly on the top of the radiator or on the header (or surge) tank.
The thermostat is located under the thermostat housing.
The thermostat regulates the flow of coolant, allowing a circulation of coolant to flow from the engine to the radiator when the engine is running at its operating temperature. But it is closed when the engine is cold to allow the engine to warm up more rapidly.
The thermostat housing is normally located on the outlet side of the coolant flow from the engine. The majority of thermostat housings used today are made from an aluminum alloy, and will corrode away instead of the engine or cylinder head. This is known as a 'sacrificial component'.
The water pump is normally bolted to the front of the engine block. The bottom radiator hose comes from the radiator and is connected to the water pump inlet.
The water pump is driven by the engine via a fan or drive belt.
As the coolant leaves the outlet of the radiator, which has removed much of its heat, the water pump forces it through the water jackets by the action of the impeller in the pump.
The cooling fan can be located on the water pump shaft, or it may be attached directly to the engine crankshaft. In most cases, this requires some engine power to drive the fan.
The blades of the cooling fan can be made of steel or plastic. The blades draw cooling air through the radiator core, thus lowering the temperature of the coolant.
On most vehicles there are two radiator hoses. A top radiator hose is attached to the thermostat housing, which allows the heated coolant to enter the top or inlet side of the radiator.
The bottom or lower radiator hose is connected between the outlet of the radiator and the inlet of the water pump.
The radiator hoses and by-pass hoses are held in position by clamps attached to the engine block or radiator assembly.
These can be spring clamps, or wire wound clamps, or worm drive clamps.
The heater hoses are normally pre-shaped for the particular make and model of vehicle you are servicing.
The construction of the heater hose is the same as the radiator hose, with a reinforcing material embedded into it.
The hot coolant comes in through the hose attached to the thermostat circuit, and as it sheds some of its heat into the vehicle, it cools down and returns to the engine via the water pump inlet.