Unfixable Oil Leak

Since I got this jeep about 3 years ago it's had an oil leak in the same spot - right at the back of the oil pan. I've tried everything and can't get it to stop or even slow down. It's a 258 with the molar EFI. I've replaced the rear main and oil pan gasket 4 times each. I checked the oil pan each time, it seemed fine, but the last time I went ahead and got a brand new oil pan. I've tried with no gasket sealant, lots of gasket sealant, and just a little gasket sealant. Nothing makes a difference. I've checked the rear main each time I pull it out and other than the first time when I didn't use the little wax paper thing to slide it in - and nicked the gasket, it's looked in perfect shape every time. I've used the fluorescent leak detector stuff to search for a leak, and it all comes from right at the back of the pan, impossible for me to tell if it's rear main or just the oil pan.

Is there anything else that could cause a leak from there? Is it possible it's a worn crank or worn main bearings or or or?

I wouldn't care a ton about fixing it, but it leaks so bad that after about 15 minutes of driving there is a little bit of spray that will find it's way to the exhaust and the whole thing smells terrible. After a 3-4 mile drive it will leave a spot on the concrete about as big as a basketball.

Any help is greatly appreciated!!

 

I wonder if there is a problem with the sealing surface of the crank? Do you know if the engine was rebuilt before you got it. Could it be ground undersize, or not concentric? Perhaps you should have someone else look at it. I know I’ve been guilty of missing things I should have caught because I was too focused on what I anticipated the problem to be. The old fresh set of eyes thing.
Good luck.

Tim

 

Could it be the valve cover gasket leaking from the rear and running down the back of the engine. That happened to mine and t thought it was the main seal until I pulled the engine for a rebuild.

 

That's a fairly significant leak. Although it's never happened to me, but just for the process of elimination you might want to either check or replace the pcv valve. I have heard that if they fail the engine can pressurize internally and force oil out of the weak point.

 

I have seen some shops that use a smoke machine and get good results. It is best to look for the simple, as in
overlooked areas first. That it leaks so much when parked means it has to have a good oil supply. Unless you
park on a pitched drive there should not be much of a leak from the rear main seal. This leads to the valve cover
as said above.

 

That's big leak.

Are you double-dog certain you are getting the correct rear main seal?

Following the genuine Factory Service Manual installation directions - carefully and completely?

 

I had a bud whos dad bought a 1970 Chevy truck brand new, 250 engine. It leaked at the rear from day one. Dealer installed 2 or 3 seals & finaly put a crankshaft in it to get it stopped

 

Check the rear of the valve cover. Mine has a slow leak and I swear it looks just like a rear main leak.
Many years ago I had a customer with a Ford PU that had a rear main leak that had been replaced numerous times. I found the PCV looked new but a generic. I installed a Motorcraft PCV valve and it fixed the leak. Later in life, I had a Mercury Bobcat (don't laugh) that leaked horribly and had bad blowby. I put a Chevy 350 PCV valve in it, just because I had one, and it helped a lot.

Just examples and thoughts that may help.

 

Thanks for the replies!!
I've used the leak detector stuff and have never seen anything that is higher than the oil pan, so I don't think it's the valve cover or head gasket - but I'll check again. I've obviously been missing something, so might as well start there!
I've changed the PCV valve, but the valve cover has a dent in it and I'm not sure it makes a great seal there. Maybe I'll work on that a bit and see if I can get it figured out. If that doesn't work I think I'll just have to take it somewhere. I haven't ever let anybody else work on the jeep - and I was hoping to be able to keep it that way, but I think I've been stumped on this one!

 

What part of CO do you live?

 

That has got to be the most frustrating thing ever! , I'm going on my second seal on my 318 mopar engine, I thought sure it was going to be ok, but NOOOOOOO
Back to you~ So yours is a 2 piece seal? and how is your main bearing? is it down to copper? how is the oil pressure?

But I have mine on an engine stand and feel I have no excuse for it to have leaked the first time. and then have it on an engine run stand.


My newest next seal:

 

Valve covers usually leak while engine running and oil splashing around.
For the leak he describes, I doubt it's the valve cover gasket.
This sounds more like the typical rear main seal leak.
But I've been wrong before.

 

Cam plug on the back of the engine?

 

I'm just east of Denver. I make it your way (your bio says Grand Mesa) about once a year for fishing, but I take my Jeep Gladiator instead of the CJ for that trip. I come close a couple times a year dragging the CJ out to Moab though!

 

I took a look again last night with some of the leak detector dye. I don't see any oil that is above the oil pan gasket. I can get a fairly decent look at the back of the motor - so I don't think it's valve cover or cam plug. I sure could be wrong, but that's what I'm seeing right now!

 

It is a 2 piece seal. I'm not sure about the main bearing. The last time I took it apart was a few months back. To be honest, I'm not sure what it looked like then, and I don't really have enough experience that I would have known if it looked worn out when I took it apart. If that was the problem, what is the solution? To me that sounds like pulling the motor to change out the crank and bearings - and at that point it might be worth it to either rebuild the whole motor or just find an LS to swap in for $1500 or so - but I don't think I really want to go that route.

 

On my second rear main, I felt like there was no reason for it to leak! For me it's not that hard to turn the engine upside down, disassemble. The second rear main was different even though the same part number. I can say it didn't leak on the second go around. I'm suspicious of the rear main seals. Also there's a bit of obsessivness, did I install it correctly, but tend to wonder after it's all installed.

http://earlycj5.com/xf_cj5/index.php?threads/155741/page-22

 

likely you could put new bearings in it with the motor in the jeep and the crank in the motor, just pull the main caps one at a time and spin in a new bearing. if the bearing is shot, the crank could wander in the block relative to the seal and lead to worse sealing properties. there's also the chance of a groove on the crank.

 

So far this sounds like the most likely after everything else I've tried. I think I'll be looking for a spare weekend or two coming up and give it a go and see if it fixes the problem. Any suggestions on what bearings to go with or are they all pretty close to equal in quality?

 

Well, I had replaced my main bearings, on the backside it said .10 over, so that's what I went with. So maybe when you have your mains back out again, you can see what's in it. I found them pretty easy to install, but I did have my engine upside down on an engine stand. I had loosened up all my main bearing caps, just a tad, wouldn't want to upset the front seal. I think that helped. I used some engine assembly lube in the process. When you get the rear main out, post a pic of it with the seal in it.