1. Disconnect the positive crankcase ventilation (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.
4. Check for a hose that collapses when blocked (vacuum applied). Replace the plugged or deteriorated hoses.
5. Allow the engine to idle at the normal operating temperature.
6. Remove the engine oil dipstick and install a vacuum gage on the dipstick tube.
7. Block off the PCV system fresh air intake passage.
8. Run the engine at 1,500 RPM for 30 seconds, then read the vacuum gage while the engine is running at 1,500 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, oil pan gasket, or other sealing areas for leaks. If the vacuum gage registers a positive pressure through the dipstick tube, check for a plugged hose or engine blow-by.

A plugged PCV hose may cause the following conditions:

A leaking hose would cause the following conditions:

The PCV system flows fresh air into the engine crankcase to dilute the unburned hydrocarbons present and route them into the intake manifold where they are consumed during the combustion process.