GM Full-Size Trucks 1970-1979 Repair Guide

PCV Valve

Print

The Positive Crankcase Ventilation (PCV) valve is located on top of the valve cover. Its function is to purge the crankcase of harmful vapors through a system using engine vacuum to draw fresh air through the crankcase. The system reburns crankcase vapors, rather than exhausting them. Proper operation of the PCV valve depends on a sealed engine. If the oil begins to form sludge, which will be obvious as it is drained, and the PCV system is functioning properly, check the engine for possible causes.

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. Check the PCV hoses for breaks or restrictions. If necessary, the hoses should also be replaced. The plastic T-fittings used in this system break easily, so be careful.

REMOVAL & INSTALLATION



See Figures 1 and 2



Click image to see an enlarged view

Fig. Fig. 1: Positive Crankcase Ventilation (PCV) locations



Click image to see an enlarged view

Fig. Fig. 2: Remove the PCV valve from the rocker arm (valve) cover

  1. Disconnect the negative battery cable.
  2.  
  3. Pull the valve, with the hose still attached to the valve, from the rubber grommet in the rocker arm (valve) cover.
  4.  
  5. Use a pair of pliers to release the hose clamp, then remove the PCV valve from the hose.
  6.  

To install:
  1. Position the new valve into the hose, then slide the clamp into position.
  2.  
  3. Install the valve into the rubber grommet.
  4.  
  5. Connect the negative battery cable.
  6.  

 
label.common.footer.alt.autozoneLogo