Coolant leakage into engine cylinders is most likely due to a defect in which component?

Coolant leakage into engine cylinders is primarily associated with a failure in the cylinder head gasket. The cylinder head gasket is a critical component that seals the space between the engine block and the cylinder head, ensuring that the coolant and engine oil remain contained within their respective passages. If the gasket fails, it can create a pathway for coolant to seep into the combustion chamber, leading to coolant entering the engine cylinders.

This situation can result in engine misfire, loss of power, and even severe engine damage if not addressed promptly. Additionally, the presence of coolant in the cylinders can lead to increased exhaust emissions and can cause a white smoke to emit from the exhaust, indicative of coolant burning in the engine.

While other components like the fuel injector, oil seal, and piston ring can cause various engine issues, they are less likely to lead to direct coolant leakage into the cylinders. The fuel injector is responsible for delivering fuel into the combustion chamber, the oil seal primarily deals with preventing oil leaks, and piston rings are designed to maintain compression and control oil consumption rather than manage coolant flow.