Crankcase Ventilation System Description: Operation
Fresh air is brought into the engine through the positive crankcase ventilation (PCV) valve (3) as long as the crankcase is under vacuum. The primary control is through the PCV orifice (2) which meters the flow into intake manifold, at a rate depending on manifold vacuum. The PCV orifice is an integral part of the camshaft cover. Under certain operating conditions, the system is designed to allow excessive amounts of blow by gases to flow through the PCV valve (1) if excessive crankcase pressure is detected. Excess blow by gases are then routed into the intake system to be consumed by normal combustion.
During normal operating conditions the PCV gases are routed using check valve (2) and the internal passage within the camshaft cover. If the engine sees excessive positive crankcase pressure check valve (1) opens and the pressure is routed to the air inlet. Check valve (1) is only used if the engine sees excessive crankcase pressure.