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. The proper operation of the crankcase ventilation (CV) system depends upon a sealed engine. If oil sludging or dilution is noted, and the crankcase ventilation system is functioning properly, check the engine for other causes and correct as necessary. This will ensure that the system functions as intended.

1. Disconnect the CV vacuum hose.
2. Start the engine.
3. Check for vacuum at the hose. If there is no vacuum, check for a plugged hose or a plugged 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 CV 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, 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 CV housing, a plugged hose or for excessive engine blow-by.

A plugged PCV housing or hose may cause the following conditions:

A leaking housing or hose would cause the following conditions: