What causes crankcase pressure?

Crankcase pressure occurs when a vehicle's breather tube is obstructed, the pistons or blower oil seals are worn or defective, the piston crown is cracked, the gaskets are defective or the vehicle has excessive exhaust back pressure. Recommended crankcase pressure amounts vary depending on the type of vehicle and engine.

When the engine's lubrication through the breather tube and the crankcase ventilator is low, the crankcase pressure can increase, causing potential damage and cracks to the vehicle's engine. The pressure of the crankcase can be checked with a manometer that is connected to the cylinder block through the oil dipstick opening.