GM Full Size Vans 1967-1986 Repair Guide

PCV Valve



See Figures 1 and 2

Click image to see an enlarged view

Fig. Fig. 1: Removing the PCV valve from the valve cover

Click image to see an enlarged view

Fig. Fig. 2: Common PCV valve hose routings

The PCV valve is located on top of the valve cover or on the intake manifold. Its function is to purge the crankcase of harmful vapors through a system using engine vacuum to draw fresh air through the crankcase. It reburns crankcase vapors, rather than exhausting. Proper operation of the PCV valve depends on a sealed engine.

Engine operating conditions that would indicate a malfunctioning PCV system are rough idle, oil present in the air cleaner, oil leaks or excessive oil sludging.

The simplest check for the PCV valve is to remove it from its rubber grommet on top of the valve cover and shake it. If it rattles, it is functioning. If not, replace it. In any event, it should be replaced at the recommended interval whether it rattles or not. While you are about it, check the PCV hoses for breaks or restrictions. As necessary, the hoses should also be replaced.