Positive Crankcase Ventilation: Testing and Inspection

PCV Valve Test:

1. With engine idling, remove PCV valve from rocker cover. If valve is not plugged, a hissing sound will be heard as air passes through the valve, and a strong vacuum should be felt when a finger is placed over the inlet of the valve.
2. Install the PCV valve, then remove crankcase inlet air cleaner. With engine idling, loosely hold a piece of stiff paper (such as a parts tag) over the opening in the rocker arm cover. After allowing about a minute for the crankcase pressure to reduce, the paper should be drawn against the opening in the rocker arm cover.
3. With engine off, remove PCV valve from rocker cover and shake the valve. A rattling noise should be heard, indicating that the valve is free.
4. If the system passes the above tests, no further service is required. If not, replace the PCV valve and recheck the system. Do not attempt to clean the PCV valve.
5. With a new PCV valve installed, if the paper is not drawn against the crankcase inlet air cleaner opening with considerable force, clean the passage in the throttle body and the [1][2]PCV hose.