Positive Crankcase Ventilation: Testing and Inspection

Crankcase Ventilation System Inspection/Diagnosis

Crankcase Ventilation (CV) System Inspection

* Test for vacuum at the vacuum hose where it connects to the crankcase ventilation valve or the cylinder head cover. There should be manifold vacuum present at the hose. If there is no vacuum, inspect for a plugged hose, leaking hose or a plugged vent adapter.
* Plug the end of the vacuum hose while the engine is running. Inspect the hose for any areas that collapse when the end of the hose is blocked. Replace the hose if it collapses when blocked.
* If oil has accumulated in the intake air duct, inspect for the following conditions:

- Plugged vacuum orifice in the crankcase ventilation housing
- Plugged or restricted crankcase ventilation housing
- Excessive crankcase pressure or blow-by, refer to Oil Consumption Diagnosis (Component Tests and General Diagnostics).

* Additional items to inspect:

- Plugged or leaking fresh air vent hose assembly or vent adapter
- Plugged or restricted passages in the throttle body
- Missing or damaged O-ring seals on the vent adapter
- Inspect the cam covers, the oil pan gasket, and other sealing areas for leaks

Results of Incorrect Operation

A plugged crankcase ventilation housing or hose may contribute to the following conditions:

* A rough idle
* Stalling or a slow idle speed
* Oil leaks
* Oil accumulation in the intake air duct
* Sludge in the engine

A leaking housing or hose may contribute to the following conditions:

* A rough idle
* Stalling
* Unstable idle speed