Description And Operation

DESCRIPTION 

The crankcase bypass diaphragm PCV system consists of the following components:

OPERATION 

The crankcase bypass diaphragm PCV system channels vapors through a separator and PCV diaphragm assembly located in the cylinder head cover / valve cover and is a serviceable part.

In a diaphragm type PCV system, a leak proof diaphragm separates the upper and lower chambers of the valve. The diaphragm is loaded by a pre-stressed spring and a hole connects atmosphere to the upper chamber. When the engine is off, there is no flow and the spring holds the diaphragm up and the valve is open.

Crankcase vapors are routed through the bypass diaphragm PCV valve. The diaphragm on a turbo engine has three connections, one outlet to the intake manifold, one outlet to the turbo (intake side), and the other inlet from the crankcase.

The valve has internal chambers. The first is the inlet that accepts the crankcase vapors coming into the diaphragm. The second is the chamber that connects the two outlets (intake) and (turbo). The crankcase vapors coming into the bypass valve are regulated by the diaphragm (4). The direction of flow out of the valve is determined by the amount of vacuum at the outlets (intake) and (turbo). If for example, the engine is operating with the throttle body in a minimally closed position, the intake collector is in strong depression. This would cause the diaphragm at the intake collector to open and the turbocharger diaphragm to close.

Courtesy of CHRYSLER GROUP, LLC

If the engine is operating in full acceleration with the throttle open, the turbocharger is sucking in a lot of air, creating a vacuum in the air inlet sleeve. In these conditions, diaphragm (2) opens the passage and the diaphragm (3) closes at the same time. Moreover, diaphragm (4) prevents the engine block from experiencing excessive vacuum. If the block vacuum exceeds a certain threshold, it potentially may allow oil to enter the air intake system.