The following upgrade works only on those 4.0L XJs that already have the HO-type valve cover. The valve covers from non-HO XJs differ and this upgrade will not work on those early ('87 through '90) 4.0L XJs/MJs. It might be possible to upgrade an earlier XJ with the late-model XJ valve cover and if anyone has done this successfully, please send us a short report and perhaps a picture too .

My '93 XJ had begun to blow oil out the valve cover air intake hose, so I removed the old hoses and valve cover to repair whatever I found. The rear valve cover fitting with the metered vacuum hole had a small cone of oil deposits built up which closed off the hole. Other than that, the inside of the valve cover looked quite clean. I have run Mobil 5W30 for the life of the engine, and for the most part, there was no sludge buildup. There was kind of a baked on oil residue in certain areas that scraped clean with a screwdriver and the little cone of particles blocking the vacuum hole. The cone wiped/crumbled off easily, but I decided to replace all the fittings and hoses anyway as the plastic hoses were brittle and the rubber fittings were rotten. I did a little research and found that 2000 XJs used a larger rear hose from the valve cover to the intake manifold, but the front hose was about the same size. A larger tube will be less prone to blockage. I also found out that the 2000 valve cover fittings won't fit in the '93 valve cover. I ended up using new '93 valve cover fittings, new '93 hose from the front of the valve cover to the air box, and a 2000 hose and intake manifold fitting to connect the vacuum to the rear of the valve cover. Also, replacing the valve cover results in some confusion as to what to do to seal it. I have heard that it is hard to get it to seal once removed. The factory recommends using a new cover with factory applied sealant! This is an expensive option. Some folks use a gasket from Napa or the like while others try silicon gasket maker. I have had poor luck with valve covers in the past, so upon recommendation of someone who said they had success, I tried Locktight 518 gasket eliminator. It is like an expensive silicon, but I tried it anyway. I used a full tube to squeeze a bead on the cleaned head and valve cover surfaces. I then placed the cover in place and bolted it down. My friend recommended using locktight threadlocker on the bolts after the gasket cured for a day, but I haven't done that yet. In fact, I haven't run the Jeep much yet, so I can't even tell you if the Gasket Eliminator was succesful. Take a look at the pics to help explain the new parts.

2000 CCV tube/manifold fittings have a larger I.D. than 1993 pieces.

From top:
A: 2000 CCV fitting/grommet/tube/manifold fitting.
B: New and old '93 CCV fitting/old tube/old manifold fitting.
C: New '93 front fitting/tube
D: Old '93 fitting/tube.
[large image]

From top:
A: 2000 CCV fitting/grommet/tube.
B: New and old '93 CCV fittings/old '93 tube.
C: New '93 breather fitting/tube.
D: Old '93 breather fitting/tube.
[large image]

Here are the part numbers and costs for the parts used:

This combination of parts yielded new tight fitting valve cover pieces, larger rear suction tube/intake manifold fitting (newest xj pieces) and stock front breather tube size which is the same as the newest XJ's.