Positive Crankcase Ventilation

Positive Crankcase Ventilation (PCV) system uses intake manifold vacuum to recycle blow-by vapors from the crankcase to the combustion chamber, where they are burned. PCV valve meters flow of blow-by vapors, according to manifold vacuum. When high amounts of blow-by gases are produced (such as worn piston rings), excess gases flow back through crankcase vent hose into the air inlet and are burned during normal combustion.