COOLING SYSTEM

How does a cooling system work?

Cooling systems are filled with a chemical coolant antifreeze that has a lower freeze point, and higher boiling point, than water.

The cooling system maintains the engine temperature and coolant temperature at the level necessary for normal operation.

In the past this was usually a green coloured fluid, however many manufacturers now use long-life coolants which may be orange, red, blue or yellow.

Coolant is forced into the bottom of the engine by a water pump – usually driven by either a timing belt or serpentine belt. The coolant then flows around the walls of the cylinders – removing heat generated through the burning of fuel. The coolant flows through the passages in the cylinder head gasket into the cylinder head, again removing heat from the top of the cylinders.

The thermostat valve keeps the coolant trapped inside the cylinder head until the coolant temperature reaches a pre-set level at which the engine runs most efficiently. At this point, the thermostat opens to allow coolant to flow into the radiator.

As air passes over the radiator, heat is transferred from the radiator to the air, lowering the temperature of the coolant, so that the cycle can start over.

A heater hose, normally connected right before the thermostat, carries some of the hot coolant to the heater matrix. The heater matrix is used to provide heat to the cabin of the vehicle. Just like the radiator, as cool air passes over the heater matrix, heat is transferred from the coolant to the air – reducing the coolant temperature and heating up the air entering the cabin. The coolant from the heater matrix then re-enters the cooling system to pass through the engine again.