What is the purpose of oil drains in a cylinder head?

• A. Distribute coolant
• B. Aid oil getting back into the crankcase
• C. Seal combustion chamber
• D. Drain oil to radiator

Answer: (B)

Oil drains in a cylinder head provide a return path for the lubricating oil that flows through the head to keep camshafts, rockers, and other overhead components properly lubricated. The drains allow that oil to flow back down into the crankcase so it can be picked up by the oil pump again, rather than pooling in the head and potentially causing oil starvation or burning. They are not for coolant distribution—that’s handled by the cooling passages. They don’t seal the combustion chamber—that’s the job of the head gasket and valve seals. They also don’t drain oil to the radiator, since the radiator cools coolant, not oil.