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Leaking oil like crazy!!


NAXJA Forum User
North carolina
Hey I have an 88 4.0 Cherokee with 169000 miles and she runs strong but I have noticed that everywhere I go I leave ALOT of oil on the pavement! I was running regular blend ever since i got it at about 167000. I heard that synthetic cleans the engine of unwanted sludge so I decide to add synthetic little by little and now my small leak has gotten massive. Also my oil pressure was schitzo..it went from 70 for a while then to 40 then back and forth between 20 and 40 and now it is on 20. I am 80%sure it is my rear main seal and was wondering if there is anyhthing I can do to at least slow it down. I want to kno if running it with a leak like this is bad beacuse I have to drive from Charlotte NC to Baltimore MD. Any response would help greatly thanks!
As long as it has good oil pressure then it's fine, but you'll want to keep a close eye on the level. Figure out how many miles you can go before it's about a quart low, and make sure you stick to stopping and adding a quart at those intervals.

What you're saying about the oil pressure seems kind of wierd though. What does it read at cold when you first start it up? How about at highway speed, and at idle? My 87 leaks like a siv from the rear main, but as long as I keep it topped off it's fine. Oil pressure is about 42-45 psi at highway speed when warm, and a little over 21-22 at idle when warm.
Since you started using synth., it probably cleaned away the crud on the old seals causing them to leak while the crud itself is clogging up the oil pump pick up screen, causing the oil pressure to drop.
You can keep topping up theoil level for a while but eventually you'll need to replace the leaking rear main. Since you'll need to drop the oil pan to do that anyway, you can also replace the old oil pump at the same time.
Make sure the leak isn't from the oil filter mount. I thought I had a rear seal leak till I replaced the 3 o-rings on the filter mount.
check out the bolts on the valve cover, they have a thing about working themselves loose and do one hell of a rear main oil leak impression, i thought my rear main was out in my cj, turned out to be valve cover, thought my rear main was going out on the xj, valve cover, and my friend was going home to change his rear main and i told him to check the valve cover first and guess what, valve cover.

similar deal happened to me. at over 100k i started using some synthetic oil and it knocked some crud loose enough to throw my oil pressure sending unit into a false reading. i changed the unit along with my rear main seal and it has been fine ever since, it's back to 60 psi on the hiway and 40 on the trail(when real hot day). sending unit much easier to change than the rear seal for sure, but it is worth it, no more oil in the driveway........