Crankcase Ventilation System Diagnosis. Cadillac Concours 1996

For 1990-2009 cars

### Functional Test of PCV Valve

If an engine is idling rough, check for a clogged PCV valve or plugged hose. Replace as required. Use the following procedure:

1. Remove PCV valve.
2. Run the engine at idle.
3. Place your thumb over the end of the valve to check for a 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 needle inside the valve. If valve does not rattle, replace valve.

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 air cleaner and is drawn into the engine through throttle body.

Proper operation of the PCV system is dependent upon a sealed engine. If oil sludging or dilution is noted, and the PCV system is functioning properly, check engine for possible cause , i.e. missing oil cap, or dipstick, infrequent oil changes, internal coolant leak, and correct to ensure that system will function as intended.