Positive Crankcase Ventilation: Testing and Inspection

Functional Check:

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 from manifold

2. Run the engine at idle

3. Place your thumb over end of valve to check for vacuum. If there is no vacuum at the 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.

With this system, any blow-by in excess of system capacity is exhausted into the intake manifold and is drawn into the engine. 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 and correct to ensure that system will function as intended.

PCV Valve System
1. Check PCV valve for correct application

2. Engine at normal operating temperature

3. Block off PCV system fresh air intake passage

4. Remove engine oil dipstick and install a vacuum gage on dipstick tube

5. Run engine at 1500 rpm for 30 seconds then read vacuum gage while at 1500 rpm. If vacuum is present the PCV system is functioning properly. No vacuum indicated the engine may not be sealed and/or is drawing in outside air. Check valve cover, oil pan gasket for leaks. If the vacuum gage registers a pressure or the vacuum gage is pushed out of the dipstick tube, check for the correct PCV valve, a plugged hose or excessive engine blow-by.