GM Cutlass RWD 1970-1987 Repair Guide

Crankcase Ventilation

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A Crankcase Depression Regulator Valve is used to regulate (meter) the flow of crankcase gases back into the engine. The Crankcase Depression Regulator Valve (CDRV) is designed to limit vacuum in the crankcase as the gases are drawn from the valve cover(s) through the CDRV and into the intake manifold (air crossover).

Fresh air enters the engine through the combination filter, check valve and oil fill cap. The fresh air mixes with blow-by gases and enters both (V8), or one (V6) valve cover. The gases pass through a filter installed on the valve cover(s) and are drawn into connecting tubing.

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 decrease, the spring pushes the diaphragm away from the top of the outlet tube allowing more gases to flow to the intake manifold.

Do not allow any solvent to come in contact with the diaphragm of the Crankcase Depression Regulator Valve because the diaphragm will fail.

Do not attempt to test these valves. Instead, follow the cleaning procedures in General Information & Maintenance if you are experiencing problems with the system.

See Figures 1, 2, 3 and 4



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Fig. Fig. 1: Diesel EGR vacuum reducer, except California



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Fig. Fig. 2: Diesel vacuum regulator valve



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Fig. Fig. 3: Diesel engine temperature sensor



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Fig. Fig. 4: Diesel EGR system, California

 
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