Stan.Shaw@Excell.Net

I suspect my rear main seal may be leaking in the race car ('80 Euro S with '86
5L bottom end) but am curious if anyone has had such a failure, and where the
oil leak is seen.

My leak is showing up on the back of the headers near the clutch housing. The
oil is seen along the seam between the block and clutch housing, which is why I
suspect the rear main seal.

Thanks!

GlenL

I had this and, in my case, the answer was "everywhere." The seal ruptured a good inch wide at about 130mph. Got a black flag, and a tow, for that one.

The replacement started to ooze a bit after a week or so. Just hadn't seated it all the way. In that case it dribbled down the block and some flowed out the front lip of the bellhousing cover and some went out the inspection hole. From there it was blowing back onto the exhaust pipes and underbody.

You should be able to ID the leak source with that lower cover off. Maybe stick a finger in the inspection hole.

The leak pattern you describe sounds more like rear cam covers.

BTW - Plenty of whoa power with the matching later-S calipers and Hawk Blues. THX!

Bill Ball

Stan:

As part of my review of replacing the seal an an automatic car, I go through the diagnosis (in the section starting with "NB: Before we get started,"). A ruptured seal is one of only 2 things that can wet the inside of the bellhousing behind the flywheel. I'm not positive the other factor is present in an 86.

http://www.billsworkshop.com/P928S4/seal/seal.htm

Stan.Shaw@Excell.Net

Thanks, removing the clutch cover requires removing the headers, so is non trivial, but I expect I will need to do so.

I can see behind the cam covers, and don't see any sign of leakage there.

I also think this problem started after some higher rpm testing. This motor has yet to see any track time.

928ntslow

I would say it's the rear main. Chances are you are getting more oil showing up on the passenger side of the clutch housing since the rotation and gravity throw it all in that direction. Of course wind turbulance under the car will spread it everywhere. I had this problem on the GTS. The good news, is getting to the rear main...not nearly as a PITA as the front.

Bill has a good write up over the task, though you have more room once the clutch, pressure plate and flywheel are removed. Getting out the old seal is rather simple, getting the new one in will be tough if you try to pound it in...not really any room for a hammer. I did it the first time and it still leaked because I was unable to seat the seal. The second time I got smart and used the fly wheel and 4 bolts to press in the seal. Worked like a charm and hasn't leaked since. Tap the seal in enough to secure it. Use 4 bolts for the flywheel in an "X" pattern and work your way around making 1/2 to 1 turn at a time in a criss cross pattern. Oh yeah, use the old seal in between the new seal and the fly wheel. This will allow you to seat the seal all the way in. Do not over tighten, just get the seal sunk in past the outer ring housing.

You should be able to knock this out in less than a day if all goes smooth...even if you are laying on your back with the car on stands.

Good luck.

Stan.Shaw@Excell.Net

Thanks Keith, it does seem to smoke more on the passenger side when I rev the motor.

Stan.Shaw@Excell.Net

Unbolted the headers....boy do I hate that task. I wonder if air tools would help....

Pulled the clutch cover, and really don't see much oil. For those that have had a rear main seal go, didn't you find quite a bit of oil inside the clutch housing? I guess it could have all dripped out since it has been days, but I am skeptical.....

Thanks!

Bill Ball

Yes, Stan, there should be fresh oil inside the housing, especially on the block below the rear main seal. If it is just old grime, then look somewhere else. However, if there is ANY fresh oil there, that's strong enough evidence. The oil from this leak will wet the back edge of the pan, but the bulk should blow back from the bellhousing.

I did not have any trouble at all removing or seating the new seal, and with a 5 speed, it should be even easier access. With any seal like this, the key is getting it started evenly. One side will tend to pop out as the other side goes in, canting the seal. Stop , reseat and start over until you get it perfectly even and check often as you press or pound it in. You can improvise a tool to press it in using some flat stock and the flywheel bolts.

I would say if there is any indication, do the seal. It's fairly easy in a 5-speed. You've already done the hard part.

Garth S

Have you lifted the air cleaner and checked the valley for oil? ( what - a 928 leaking in the valley!! ) If oil accumulates here, it will appear where described, and may run into the bell housing through the opening where the release arm ball stud sits.

Bill Ball

The S4s have a drain hole in the valley that exits the block immediately over the rear main seal, perfectly emulating a rear main seal leak.

Stan.Shaw@Excell.Net

Thanks for the replies.

Compare to your average street car, mine is relatively clean, as the motor has been in and out 3 times in the last couple of years...

I dropped the clutch, and there really isn't much oil inside the clutch housing.

I think Garth's thought may be correct. I did have an oil leak at the oil filler gasket base, which put oil in the valley. I thought got I it all cleaned up, but when I ran the car again it still was smoking badly. With a manual, the clutch arm extends through the housing on to a pivot, and that opening would allow oil to drop into the clutch housing, and of course then get sprayed everywhere, mimicking a rear main seal.

With the top and bottom open I should be able to clean more thoroughly, and put it back together. Eventually I will consider removing the headers a trivial item, right......

Garth S

I snugged up the two oil filler bolts over the oem cork gasket in the 16v - and it worked ( the T-stat housing was not going to come off easily): The valley was then treated to a generous spray of citrus cleaner ('orange blaster'), and hosed clean - remarkable, that stuff - and it's still dry ... but I had oil inside and around the bell housing.

mark kibort

Bill, and others, how far do you push in that rear main seal?? in the manuals, it only shows tools to install, but when we did the 5 liter, and put the seals on the crankbefore we put the two engine halves together, it seemed the seal should go all the way in. now that i remember it, does the seal go all the way into the seal area, or just flush with the outer surface?? i know the front only was in flush, but the rear i cant remember. i think it was in pretty far and i thought it was too far. any issue with the seal being seated too far in the seal housing, or should it ONLY be flush, or does it matter? (when the block is a about to be assembled, the seal looks like it should go to an area that stops it. after putting the block together, this makes the seal sit in the block about 5mm in passed being flush with the flush surface)

Mk

Bill Ball

As I recall it seated (bottomed) and was just ever so slightly below the lip of the surrounding boss and a bit more below the level of the crank face. The removal notch is deep enough that the seal needs tio be seated well to avoid a leak there. Here is a pic of the seal.

mark kibort

nice picture. so what if the seal is about 2-3mm farther in? I think thats where it actually bottoms out. I still think there is a long enough crank area for the crank to ride on the seal in so it hopefully is not an issue.
just wondering if that could cause a leak if assembled with the seal even farther in than your pic.
by the way did i mention..... great picture!

MK