Which component is responsible for circulating coolant in the engine?

The water pump is the key component responsible for circulating coolant throughout the engine. It ensures that the coolant flows between the engine, the radiator, and the heater core, facilitating effective heat transfer. By maintaining proper coolant circulation, the water pump helps regulate engine temperature, preventing overheating and ensuring optimal performance.

In a typical engine cooling system, when the engine operates, the coolant absorbs heat from the engine and then flows to the radiator. The water pump creates the necessary pressure to push the coolant through the system, allowing it to dissipate heat before returning to circulate again. This continuous movement is vital for maintaining the engine at its designed operating temperature, which is crucial for efficiency and longevity.

The other components mentioned, such as the thermostat, play a different role by regulating coolant flow based on temperature but do not circulate the coolant themselves. The radiator cap serves to maintain pressure in the cooling system, preventing coolant from boiling and enabling higher temperature operation. The cylinder head is part of the engine where combustion occurs and doesn't have a direct role in coolant circulation.