Positive Crankcase Ventilation: Description and Operation

PCV System Schematic:

PURPOSE
System prevents engine blowby gases from escaping to atmosphere.

LOCATION
PCV valve is in right valve cover.

OPERATION
The PCV valve is operated by intake manifold vacuum and crankcase pressure. When the engine is running at idle, manifold vacuum is high and there is little blowby past the pistons. The PCV valve is slightly opened and a small amount of blow-by gas is drawn into the combustion chamber. At high engine speeds and loads, manifold vacuum is low and there is much more blowby. The PCV valve opens farther and a larger amount of blow-by gas is drawn into the combustion chamber.