- When the engine overheats, the cylinder head can expand, causing damage to the head gasket (a seal between the top and bottom of the engine). This can affect engine combustion and/or cause coolant to mix with engine lubricant. In some cases overheating will crack the cylinder head.
Pistons and Rings
- With a bad head gasket, coolant can leak into the cylinders, diluting the oil and eventually damaging the pistons and rings. Coolant in the cylinders can also destroy the oxygen sensor, the catalytic converter and/or cause the engine to go into vapor lock, which will prevent it from starting.
- If coolant leaks into the crankcase of the vehicle it will cause damage to the bearings and contamination of the engine's oil.
- Fluid leaks can occur in the lines carrying automatic transmission fluid through the transmission cooler. This will damage the transmission.