The Positive Crankcase Ventilation (PCV) valve regulates crankcase (oil pan) ventilation during the various engine operating conditions. At high vacuum (idle speed and partial load range) it will open slightly and at low vacuum (full throttle) it will open fully. This causes vapor to be removed from the crankcase by the engine vacuum and then sucked into the combustion chamber where it is burned.REMOVAL & INSTALLATION
See Figures 1 through 5Carbureted Engines
- Check the ventilation hoses for leaks or clogging. Clean or replace as necessary.
- Locate the PCV valve in the valve cover. Remove the valve.
- Blow into the engine end of the valve. There should be a free passage of air through the valve.
- Blow through the intake manifold side of the valve. There should be little or no passage of air through the valve.
- If the PCV valve failed either of the preceding two checks, it will require replacement.
- Install the valve firmly into the valve cover. Connect the hose(s) and make sure there are no leaks around the hose connections.
- The PCV is easily checked with the engine running at normal idle speed (warmed up).
- Remove the PCV valve from the valve cover or intake manifold, but leave it connected to its hose.
- Place your thumb over the end of the valve to check for vacuum. If there is no vacuum, check for plugged hoses or ports. If these are open, the valve is faulty.
- With the engine off, remove the PCV valve completely. Shake it end to end, listening for the rattle of the needle inside the valve. If no rattle is heard, the needle is jammed (probably with oil sludge) and the valve should be replaced.
An engine which is operated without crankcase ventilation can be damaged very quickly. It is important to check and change the PCV valve at regular maintenance intervals.