Functional Check

FUNCTIONAL CHECK
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 crankcase ventilation system is dependent upon a sealed engine. If oil slugging or dilution is noted and the crankcase ventilation system is functioning properly, check engine for possible cause and correct to ensure that system will function as intended.
If an engine is idling rough, check for a clogged crankcase ventilation valve, dirty vent filter, air cleaner element, or plugged hose. Replace as required. Use the following procedure:
1. Remove crankcase ventilation valve from rocker arm cover.
2. Operate engine at idle.
3. Place your thumb over end of valve to check for vacuum.
If there is no vacuum at valve, check:
- For plugged hoses.
- Manifold port.
- Crankcase ventilation valve.

4. Turn "OFF" the engine and remove crankcase ventilation valve. Shake valve and listen for the rattle of check needle inside the valve. If valve does not rattle, replace valve.