Positive Crankcase Ventilation: Testing and Inspection

Crankcase Ventilation Valve Cross Section:

TEST DESCRIPTION
If an engine is idling rough, check for a clogged Positive Crankcase Ventilation ([1][2]PCV) valve or plugged hose. Check PCV part number to be sure the correct PCV is installed. Replace as required. Use the following procedure:

1. Remove PCV valve from rocker arm cover.
2. Run the engine at idle.
3. Place your thumb over end of valve to check for vacuum. If there is no vacuum at valve, check for plugged hoses or manifold port or PCV valve. Replace plugged or deteriorated hoses.
4. Turn "OFF" the engine and remove PCV valve. Shake valve and listen for the rattle of check needle inside the valve. If valve does not rattle, replace valve.
5. With this system, any blow-by in excess of the system capacity (from a badly-worn engine, sustained heavy load, etc.) is exhausted into the inlet duct and is drawn into the engine.