Massive Oil Leak or Massive Blowby ?

My XJ leaked a little bit of oil years ago when I first got it. My dad looked at it and said that he would suggest changing the valve cover. I did that and it seemed to go away. About a year ago I noticed oil on the top of the vavle cover and some on the side. I figured it was the gormets for the CCV tube and the oil breather going to the air filter box. About 2 weeks ago I noticed a slightly large pubble of oil in the drive way. Looked under the truck and noticed the bottem of the trans and engine were covered in oil. I first thought that the rear main seal went. I went to where my father works (hes a diesel mechanic) and put the truck up on lift and steamed bottem of the engine and trans down. Then put it down steamed the engine compartment and ran it for about 20 minutes. Put it back up on the lift and it was still clean. Went home and notice that it left another puddle again and that everything was starting to get oil covered agained. I don't think the rear main seal is leaking because there seems to be oil on the top of the bell housing too. I wondering if it not blowby and only happens when its at high rev's from driving... Anyone got any ideas. I'm gonna change the valve cover and replace the gormets as soon as I can get them. Oh, and I changed the air filter and there wasn't that much oil on it...

Thanks,
Doug
P.S. 90 XJ 2.5 4WD

Hard to say without seeing it. You could try putting some tracer dye in the oil first, that might help before you start just throwing parts at it.

I had the same problem and it turned out to be a cross threaded valve cover bolt against the firewall and a bad gasket. Solved it bt removing the cover, replacing the gasket and started the problem bolt first, just enough to make sure it was started strait and then tightened the bolts from the center out and that took care of it. Any oil in the aircleaner indicates a problem but with a small amount in the filter it may br just a vacuume leak. I have bad blowby on my 87 MJ even after replacing every vacuume line I found; the problem is so bad it drains out of the airbox after prolonged highway runs.

oil filter adapter o rings.
That's a pressurized passage, so high oil pressure might make it show up. Also known to look like a rear main as the oil drains down to the bottom of the pan and is pushed back by highway speed airflow. Set of o rings will set you back about $10 at the dealer.

Thanks 87manche... A buddy of mine told me that too. I steam cleaned everything last night again and then went 10 miles up one of the local interstates and back down... The engine and tran had oil on it but not a whole lot like beforebut still a decent amount... I'm beginning to think that I have multiple little leaks. I notieced that the oil pressure sending unit its leaking and that the vavle cover was also. I took all the vavle cover bolts out and retightened them from the center to front and back... I did figure this much out and that that my dad and all his mechanic buddies agree that the rear main seal isn't leaking... Which makes me happy as the XJ has almost 204k on it ! Other then the oil leak(s) it still runs strong !

Doug