I have a 1989 Jeep Cherokee Pioneer 4x4 4.0L and it has an oil leak pretty bad. It seems to only leak oil for a short time after running the tank and the seems to be mostly grime and oil on the passenger side of the engine all the way down.
Also when I am driving the oil pressure gauge goes to like 70, and if I put more oil in, it will got back to 40. When it is just idling it will be 40, but again, driving it will be high.
More then likely its the valve cover gasket but keep an eye on the temp and keep checking the oil. If it seems to be coming from lower, like around the head it could be a head gasket but unlikely. Another major culprit is the oil sending unit o-ring. More then likely its the VCG.
Im not sure about the oil pressure issue. Im sure its related but a more experienced Jeeper will likely be able to tell you about that.
My VCG is leaking, not very bad but still leaking, and have no issues with the pressure.
Mine idles at 40 and goes to about 50 when driving.
Start at the top and work your way down. Oil , like *****, flows downhill. Ask any plumber. If you are 100% sure the valve cover gasket isn't leaking, look at your oil pressure sender and don't forget the notorious leaker, the oil filter adapter. BTW, did you run your fingers behind and below the rear of the valve cover when you were inspecting? Leave the rear main seal for absolute last. Concentrate on everything above oil pan level for now. I'd put my money on the oil sender and/or oil filter adapter. But more importantly, you need to put your eyes and hands on your Jeep and check it out yourself.
Take a gander around the oil filter. That's where the oil sending unit is, you know that thing with the wire going to it so it can SEND a signal to the gauge on your dash. That's also the area where the oil filter adapter is, the deal your oil filter screws on to. These are very common areas to have leaks and are easily fixed. They must be addressed first before diving into a rear main seal replacement/
I might be ignoring whatever you found here, but make sure your the oil breathing line from the valve cover to the air box is not kinked. I kinked one of the lines going to the air box while messing with the air filter once, I think it was the big one, and it started puking oil.
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2001 Jeep Cherokee 4.0 L Limited, White. Bought in Grangeville, ID 06/11/08. Stock everything.
1998 Jeep Wrangle 4.0 L, Green. Bought in Nampa, ID 02/21/09
1988 Jeep Cherokee 4.0 L, White. Bought in Vancouver, WA in 2003. 1st Jeep, White. Bought with 3" lift, added Pacesetter header and 40 series Flowmaster