Crankcase Ventilation Systems: Operation

Crankcase vapors and blow-by gases from the crankcase are drawn, by engine vacuum present at the air cleaner, into the cylinder head cover, through the metered opening (or PCV valve) and into the hose which directs the gases to the air cleaner. Here, the vapors and gases mix with the fresh incoming air and are drawn into the engine with the air/fuel mixture to be burned. This reburning of the vapors lowers the emission output of the engine.