Closed Crankcase Ventilation System: 4.0L
Closed Crankcase Ventilation (CCV) system is used on the 4.0L engine. CCV system performs same function as a conventional PCV system, but does not use a vacuum controlled PCV valve. CCV system uses a fixed orifice fitting. Before attempting diagnosis, be sure locations of fixed orifice fitting and air inlet fitting have not been inadvertently exchanged. See Fig 1. The fixed orifice fitting is light Gray in color and is located at rear of valve cover. The air inlet fitting is Black in color and is located at front of valve cover.
- Remove fixed orifice fitting from valve cover and leave tube attached. Start engine and let idle. A hissing noise should be heard from fixed orifice fitting. Also, a strong vacuum should be felt with a finger placed at fitting inlet. If vacuum is not present, remove fitting. If vacuum is now present at tube, replace fixed orifice fitting. Do not attempt to clean fitting. If vacuum is not present at tube, go to next step.
- Check tube for kinks or obstruction. Clean tube fitting at intake manifold, if necessary. A 1/4" drill may be used (by hand) to dislodge any solid particles. Reinstall fixed orifice fitting and tube. Disconnect air inlet fitting and hose from front of valve cover.
- Hold a piece of stiff paper loosely over opening in valve cover. Allow engine to idle for one minute so crankcase pressure can reduce. Paper should be drawn against rubber grommet in valve cover by vacuum in crankcase. If vacuum is not present, check breather hoses/tubes/lines for restrictions or obstructions. After testing, reconnect all system hoses/tubes/lines.