What does a head gasket do?

• A. Seals the combustion process and prevents coolant and oil from mixing.
• B. Seals the exhaust outlet.
• C. Regulates air intake.
• D. Provides structural support for the cylinder head.

Answer: (A)

The head gasket sits between the engine block and the cylinder head and its job is to seal the combustion chamber so the engine maintains compression. It also seals the coolant passages and oil passages to keep coolant from mixing with oil. This dual sealing must withstand high pressures and temperatures. If it fails, you can lose compression or see coolant enter the cylinder or oil contaminate the cooling system. The other options don’t fit: the exhaust outlet is sealed by an exhaust gasket, the intake system handles air flow regulation, and structural support for the cylinder head comes from the bolts and block design, not the head gasket.