Positive Crankcase Ventilation: Testing and Inspection

Crankcase Ventilation System Inspection/Diagnosis

Special Tools
- J 23951 Valve Manometer

1. Verify the air cleaner is not plugged.
2. Remove the oil level indicator. Install a J 23951 or equivalent.
3. Start the engine.
4. Check for a slight vacuum at idle. The vacuum level should be less than 5 inches.
5. If vacuum is equal to or higher than 5 inches, inspect and verify the clean air hose from cam cover to air intake is not blocked or kinked.
6. If vacuum is in the normal range, block or pinch off the clean air hose. The clean air hose is the hose between the cam cover and air intake system. Vacuum should increase on the manometer. If held too long, vacuum will be drawn through the crankshaft seals creating a sucking sound.
7. If vacuum does not increase, the orifice in the intake manifold could be plugged.
8. If there is zero vacuum or pressure, verify compression of the engine.
9. If compression is normal, check for a blocked orifice at the intake manifold. Clean the orifice.