Positive Crankcase Ventilation: Testing and Inspection

Results of Incorrect Operation
A plugged crankcase vent tube assembly may cause:
- Rough idle.
- Stalling or slow idle speed.
- Oil leakage.
- Oil in air cleaner.
- Sludge in engine.
A leaking crankcase vent tube assembly may cause:
- Rough idle.
- Stalling.
- High idle speeds.

Functional Check
With these systems, any blow-by in excess of the system capacity (from a badly worn engine, sustained heavy load, etc.) is exhausted into the air cleaner and is drawn into the engine.
Proper operation of the PCV system is dependent upon a sealed engine. If oil sludge or dilution is noted and the PCV system is functioning properly, check the engine for possible cause and correct to ensure that the system will function as intended.

If an engine is running roughly, check for a clogged crankcase vent tube assembly. Replace as required. Use the following procedure:
- Remove the crankcase vent tube assembly from the rocker arm cover.
- Run the engine at an idle.
- Place your thumb over the inlet end to check for vacuum. If there is NO vacuum at the inlet end, check for a plugged crankcase vent tube assembly or manifold port. If necessary, clean crankcase vent tube assembly with mineral spirits.