Positive Crankcase Ventilation: Testing and Inspection

Crankcase Ventilation System Inspection/Diagnosis

1. Disconnect the PCV 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 the deteriorated hoses.
4. Allow the engine to idle at normal operating temperature.
5. Remove the engine oil dipstick and install a vacuum gage 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 vacuum gage while engine is running at 1500 RPM.
^ If vacuum is present, this indicates that the crankcase ventilation system is functioning properly.
^ If no vacuum is indicated, 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 gage registers a pressure, or if a vacuum gage is pushed out of dipstick tube, check for a plugged PCV port, a plugged hose or an excessive engine blow-by.