Positive Crankcase Ventilation: Testing and Inspection

Crankcase Ventilation System Inspection/Diagnosis (With Turbocharger)

Special Tools

J 23951 Valve Manometer

1. Verify clean air cleaner.
2. Verify oil fill cap is in place.
3. Verify oil level indicator is installed.
4. Remove the oil level indicator. Install a manometer J 23951, or equivalent, into the oil level indicator tube.
5. Start the engine.
6. The vacuum of the column of water at idle should be from 3-4 1/2 inches column height.
7. If vacuum is higher inspect and verify the clean air hose from cam cover to air inlet is not blocked or kinked, and the check valve on the clean air hose is open when vacuum from the engine is applied.
8. The hose from valve cover to the turbo is also for the positive crankcase ventilation (PCV) and is used for PCV flow under normal operation and only PCV flow during turbo boost conditions. If the hose is plugged, this will raise vacuum. Diagnosis can be done by removing the turbo side of the hose and start the engine for a few seconds. This should create a large air leak and erratic idle showing there is air flow. If the hose is blocked manually, vacuum will increase.
9. If vacuum is in 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 to approximately 5 inches on the manometer. If held too long, damage could result to the sealing system.
10. If vacuum does not increase, the orifice with check valve in the center of the intake manifold face could be plugged.
11. If there is zero vacuum or pressure, verify compression of the engine.
12. If compression is normal, check for a blocked orifice with check valve at the intake manifold clean orifice.