A cars radiator is a central part of the engines cooling system. Responsible for removal of heat from the engine coolant, the radiator system cools the liquid by allowing fresh external air to pass over a network of thin pipes, losing heat to the atmosphere.
Driven by the water pump the coolant circulates around the cooling system travelling through the engine and out via hoses or pipes to the radiator. The radiator acts as a heat exchange removing unwanted heat from the coolant before passing it back to the engine where it then runs back around the system.
A cars radiator cap is used to top up the coolant level of the cars cooling system. It also incorporates a pressure relief valve allowing any excess pressure or steam to escape in the event of overheating.
When replacing a lost or damaged cars radiator cap, care should be taken to ensure that the new item has the correct that pressure rating for the car.