In cars with a liquid-cooled internal combustion engine a radiator is connected to channels running through the engine and cylinder head through which a liquid (coolant) is pumped. This liquid is typically a half-and-half mixture of water and ethylene glycol or propylene glycol. This mixture is commonly referred to as antifreeze.

The radiator transfers the heat from the fluid inside to the air outside, thereby cooling the engine. Radiators are generally mounted in a position where they will receive airflow from the forward movement of the vehicle, such as behind the grill. Where engines are rear or mid-mounted, it's usually still necessary to mount the radiator behind the front grill, so as to achieve sufficient airflow, even though this requires long coolant pipes.

Radiator Construction

Automobile radiators are constructed of a pair of header tanks, linked by a honeycomb core. This core is usually made of stacked layers of thin metal, pressed to form channels and soldered or brazed together. For many years radiators were made from brass or copper cores soldered to brass headers. Modern radiators save money and weight by using plastic headers and may use aluminum cores. This construction is less easily repaired than traditional materials. Vintage cars may have used radiator cores made from coiled tube, a less-efficient but simpler construction.