K 3500 Truck 4WD V8-393 6.5L DSL Turbo (1993)
Positive Crankcase Ventilation: Description and Operation
Crankcase Vapor Flow
PURPOSE
The crankcase ventilation system is designed to reduce the crankcase pressure at idle. This lower pressure reduces engine oil leaks.
CDR Valve Operation
OPERATION
The Crankcase Depression Regulator (CDR) valve is used to regulate (meter) the flow of crankcase gases back into the engine. The valve is
designed to limit vacuum in the crankcase as the gases are drawn from the right valve cover, through the valve, and into the intake manifold (air
crossover).
The intake manifold vacuum acts against a spring loaded diaphragm to control the flow of crankcase gases. Higher intake vacuum levels pull the
diaphragm closer to the top of the outlet tube. This reduces the amount of gases being drawn from the crankcase and decreases the vacuum level in
the crankcase. As the intake vacuum decreases, the spring pushes the diaphragm away from the top of the outlet tube allowing more gases to flow
to the intake manifold.
