What is the purpose of the radiator in a vehicle's cooling system?

The radiator dissipates heat from the engine coolant (antifreeze) into the surrounding air. Hot coolant from the engine flows through the radiator's thin tubes and fins, where airflow — aided by the cooling fan — removes the heat before the cooled coolant returns to circulate through the engine again. The water pump moves the coolant, and the thermostat regulates its flow to maintain proper operating temperature. A failing radiator or low coolant can cause the engine to overheat. The radiator's heat-dissipating role is a key part of the cooling system.