What is blow by on a diesel engine?

Blow by is a common issue that occurs in diesel engines. It is the result of combustion gases that escape from the combustion chamber and enter the engine crankcase. In normal conditions, the blow by gases are expelled from the engine through the exhaust system, but when the pressure inside the engine gets too high, the gases can leak past the piston rings and enter the crankcase.

Blow by can indicate numerous problems in diesel engines, including worn piston rings, worn cylinder walls, damaged valve guides, and malfunctioning crankcase ventilation systems. The presence of blow by can cause a drop in engine power, reduced fuel efficiency, and increased oil consumption.

If not addressed, the blow by can also lead to more severe engine damage by causing increased wear on the engine components or triggering expensive repairs like overhauling the engine.

To reduce the blow by effect in a diesel engine, regular maintenance is recommended. This involves inspection of the crankcase ventilation system, piston rings, cylinder walls, and valve guides, allowing it to perform efficiently, thus avoiding major damage in the engine.