The crankcase ventilation system is designed to reduce the crankcase pressure at idle. This lower pressure reduces engine oil leaks. The system consists of a crankcase depression regulator valve located on the right valve cover (figure 1).
The crankcase depression regulator (CDR) valve is used to regulate 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 (figure 2).
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 (figure 3). For information about the Diagnostic Trouble Codes (DTC), refer to the Driveability, Emissions and Electrical Diagnosis Manual, GMT/95-CK-2.