Which cooling method uses coolant circulated through passages in the engine to remove heat?

• A. Air cooling.
• B. Oil cooling.
• C. Liquid cooling.
• D. Direct exhaust cooling.

Answer: (C)

Liquid cooling uses a liquid coolant circulated through passages in the engine (water jackets around the cylinders and through the block) to absorb heat from the metal surfaces and carry it away to a radiator or heat exchanger. This setup matches the description in the question, where coolant travels through engine passages to remove heat, providing uniform temperature control and effective cooling in tightly built engines.

Air cooling, by contrast, relies on fins and ambient air to remove heat directly from the engine surfaces, not by circulating a liquid through internal passages. Oil cooling uses engine oil to transfer heat, but the primary heat removal isn’t the coolant moving through engine passages in the same way as liquid cooling. Direct exhaust cooling isn’t a standard method for transferring engine heat via a circulating coolant.