Positive Crankcase Ventilation System

The crankcase ventilation system is used to consume crankcase vapors in the combustion process instead of venting vapors to the atmosphere. The system consists of two circuits, a primary (part load) and a secondary (high load) circuit. In both circuits the gases and oil vapors from the crankcase are returned via an internal ventilation into the camshaft cover that has an internal oil separator. The separated oil from the blow-by gases flows back to the camshaft area through the oil drain valve. Inside the cam cover the gases are then separated into both circuits. The primary check valve is positioned inside the cam cover as part of the primary circuit which prevents the crank case from pressure increase under turbo boost conditions. As a part of the secondary circuit the secondary check valve is positioned inside the cam cover. It prevents a bypass of the closed throttle at idle or coast down.