I've changed all the usual seals and gaskets (valve cover, oil pan, RMS, oil filter adapter o-rings, and both diffs) i still need to do the transmission pan and filter.

but the problem im having is after driving extensively (45min-1hr) on the highway (70-80 MPH), the engine temp gauge rises from 210 to the next notch and starts spewing oil all the way to the rear of the vehicle. ive tried to trace down the leak for weeks now.
i cant tell if its oil or trans fluid but im almost certain its oil. i changed the RMS thinking it had blown, but im having the same issue. i need this car to be sound as i have a long highway trip coming up in a couple weeks as im separating from the military and heading home. so any help is appreciated.
the jeep is lifted 4.5in and has 32's and have not had the time or money yet for a re-gear so i know there is more stress on the engine. but its keeping oil pressure when this happens, at least the gauge says so.

i thank and appreciate everyone ahead of time for taking their time to help!

 

Have you crawled underneath with the engine running? Use wheel chocks if you do that.

 

Yeah, I have several times. It only seems to leak really bad while on the highway. After I'm off it stops

 

Please explain what you mean by "spewing oil". Where is it coming from?

Also, check your oil level.

By the way, you say you have an SJ. This is the forum for Cherokees. You have a Grand Cherokee. The forum for those vehicles is here.

 

I just wiped everything down and went for a drive, and the only place there seems to be oil right now is the bottom of the bell housing inspection plate bolts. Please don't tell me that's the rear main seal again, I just changed it. I didn't bend, rip, or scrape it.

 

I do have a 2000 XJ Sport 4.0 with the AW4. I may have put a typo.

but by spewing oil, I mean at highway speeds there is oil going all the way to the back of the vehicle, the gas tank is covered, and there is some on the back windshield from the updraft.

 

I just double checked oil, trans and coolant levels, they're all good?

 

How many miles on your motor?
Sounds like your crank case pressure is getting too high when the engine is working hard. This can happen when wrings are getting worn out and blow-by contributes to the crank case pressure. Typically the PCV valves help to alleviate this pressure, so you will want to check those for blockages or poor function. If the pressure is not alleviated it can cause oil to blow out via seals, or even blow the oil cap off, or blow oil up the through the dipstick.


btw, my friend has an old v6 Isuzu Trooper with worn out rings (he's swapping motors soon), and the crank case pressure is getting too high. So the other night he took me for a quick drive and showed me what its like to blow the oil cap off. We simply drove until things warmed up, and then he poured the coals on (perhaps 4500-5000 rpm for about 30 seconds)...and boom! Smoke every where as the oil spewed all over the manifold. He keeps his oil cap on a zip tie so that he doesn't lose it when this happens.

 

Wonder when installing the RMS if he forgot or damaged the oil pan support.

 

theres roughly 157,xxx on it currently. The PCV valves on the valve cover were just replaced with these
https://www.oreillyauto.com/shop/b/filters-16470/pcv-valve-12021/fc6667133011/2000/jeep/cherokee?q=PCV+Valve

unless they're the wrong ones then I don't see them being the issue. The piston rings are a possibility, but I figured the engine would be running pretty rough at that point.

 

Worn out rings don't necessarily cause rough running. My friend's Trooper runs pretty well. The crank case pressure problem only happens to him when he pushes it a little extra hard.


But the other posters here could be right as well. If there is a weakness in the seals, or the way things were installed, at high speeds (high engine loads) the crank case pressure will be higher and will expose that problem. I just wanted to make sure you checked your PCV valves as a simple obvious step. Sounds like you are on top of that already.

 

Some of that was dated when I pulled it off. The rubber was cracked and hard, so it crumbled when I took the bolts out. If it's that I'd be surprised but happy. I didn't think it really sealed any pressure in

 

Check the rear valve cover bolts......

 

If blow-by is suspected as previous posts mention, oil should be evident in air filter box and filter.

 

Exactly.....