My old beater Jeep (winter driving and trips to the home improvement stores) suffered from a common problem. Starting around model year 1987 the 4.0L Jeeps used a CCV (crankcase ventilation system) instead of a PCV (positive crankcase ventilation) valve. The difference being that the CCV is a "closed" system on the Jeep 4.0L requiring two ports in the valve cover. One large hose was for intake/return air from the airbox and one tiny (inside diamter of the tube is smaller than #2 pencil lead) tube for the crankcase gases to escape into the intake manifold.
The problem with the system is that the CCV valve (which is inside and built in to the valve cover -a nonserviceable item unless the entire valve cover is replaced) often got clogged up no matter how good the maintainence on the vehicle. This causes gases and oil mist to flow backwards through the system (it has to have some way to escape) through the larger tube and into the airbox fouling the filter with oil.
I replaced all the hoses in the CCV system about 2 years ago (~$115), but it kept fouling the air filter. I was going to break down and buy a new valve cover (at the cost of $200) but ran across a recommendation on a jeep related site buried within the forums there.
The solution is to remove the grommet on the valve cover (for the small line) and replace it with a grommet for a 1985 CJ7 along with the PCV valve for the CJ7. Prior to replacing the grommet, you must bend a metal tang inside the valve cover using a screwdriver. This tang is what forms the "spring" in the built in CCV valve. Bending it up, opens the valve all the way permanently.
Next, take a 3/8 inch quick connect air chuck (the kind you screw into a blow-gun or tire chuck for use on an air compressor equipped with quick connect fittings) and replace the screw in nipple on the manifold (where the original tube attaches) with the air chuck. The chuck is an exact fit (threading and length)but has a much larger internal diameter for the crankcase gases to flow. Finally run a section of 3/8 inch fuel line from the newly installed PCV valve to the new air chuck nipple you screwed into the intake manifold. Attach a hose clap at each end of the fuel line and you're done.
I just completed this permanent fix for the idiotic and horribly designed system Jeep/AMC/Chrysler designed way back in the 80s. It works like a dream. No more blow back into the air box.
Total cost for this fix was $15 and that included a new air filter.
The problem with the system is that the CCV valve (which is inside and built in to the valve cover -a nonserviceable item unless the entire valve cover is replaced) often got clogged up no matter how good the maintainence on the vehicle. This causes gases and oil mist to flow backwards through the system (it has to have some way to escape) through the larger tube and into the airbox fouling the filter with oil.
I replaced all the hoses in the CCV system about 2 years ago (~$115), but it kept fouling the air filter. I was going to break down and buy a new valve cover (at the cost of $200) but ran across a recommendation on a jeep related site buried within the forums there.
The solution is to remove the grommet on the valve cover (for the small line) and replace it with a grommet for a 1985 CJ7 along with the PCV valve for the CJ7. Prior to replacing the grommet, you must bend a metal tang inside the valve cover using a screwdriver. This tang is what forms the "spring" in the built in CCV valve. Bending it up, opens the valve all the way permanently.
Next, take a 3/8 inch quick connect air chuck (the kind you screw into a blow-gun or tire chuck for use on an air compressor equipped with quick connect fittings) and replace the screw in nipple on the manifold (where the original tube attaches) with the air chuck. The chuck is an exact fit (threading and length)but has a much larger internal diameter for the crankcase gases to flow. Finally run a section of 3/8 inch fuel line from the newly installed PCV valve to the new air chuck nipple you screwed into the intake manifold. Attach a hose clap at each end of the fuel line and you're done.
I just completed this permanent fix for the idiotic and horribly designed system Jeep/AMC/Chrysler designed way back in the 80s. It works like a dream. No more blow back into the air box.
Total cost for this fix was $15 and that included a new air filter.