Positive Crankcase Ventilation: Testing and Inspection

With this system, any blow-by in excess of the system capacity (from a badly-worn engine, a sustained heavy load, etc.) is exhausted into the intake manifold and is drawn into the engine. A 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 the engine for other causes and correct as necessary in order to ensure that the system functions as intended.

FUNCTIONAL CHECK
Functional Check of the Positive Crankcase Ventilation (PCV) System

1. Disconnect the PCV vacuum hose.
2. Start the engine.
3. Check for vacuum at the hose. If there is no vacuum, check for a plugged hose or manifold port. Check for a hose that collapses when blocked (vacuum applied). Replace the plugged or deteriorated hoses.
4. Allow the engine to idle at the normal operating temperature.
5. Remove the engine oil dipstick and install a vacuum gauge on the dipstick tube.
6. Block off the PCV system fresh air intake passage.
7. Run the engine at 1500 RPM for 30 seconds, then read the vacuum gauge while the engine is running at 1500 RPM.


If a vacuum is present, this indicates that the crankcase ventilation system is functioning properly. No vacuum indicates that the engine may not be sealed and is drawing in outside air. Check the valve covers, the oil pan gasket, or other sealing areas for leaks. If the vacuum gauge registers a pressure or if the vacuum gauge is pushed out of the dipstick tube, check for a plugged PCV housing, a plugged hose or an excessive engine blow-by.

RESULTS OF INCORRECT OPERATION
A plugged PCV housing or hose may cause the following conditions:

^ A rough idle
^ Stalling or a slow idle speed
^ Oil leaks
^ Sludge in the engine.

A leaking housing or hose would cause the following conditions:

^ A rough idle
^ Stalling
^ A high idle speed