Replaced rear main seal on 3.0 and have a leak
 

I've mentioned in other threads that I was doing a ton of work to my X5 (3.64 differentials, single-mass flywheel conversion, trans detents, oil pan gasket, etc.). Well, I thought I was done, but now it looks like I have to go back in for a botched rear main seal replacement that I did 'while I was in there'.

I just bought the seal only (corteco) and not the whole kit with the carrier and bolts, etc. I carefully tapped the new seal in flush with the face of the carrier, just like the original. I used a new seal (the metal one) that goes behind the carrier, oiled the seal and crankshaft, and used the plastic 'installation tool' to guide the seal while sliding it on. I cleaned the threads (male & female) on those two lower bolts that go into the oil sump and used blue loctite on them to seal the threads.

I thought I did a good job, but I've got a pretty good drip now. I blotted the oil droplets and didn't get any more forming while the vehicle sat for about 2 hours. Then I drove the vehicle out of the garage and then back in, and I had oil drops forming (sort of from the big bellhousing bolt on the right on down to the long vertical oil pan bolt in the pic).

Does this indicate it's not the oil pan gasket or that lower bolt that goes into the sump? If it's only leaking while the engine's running, that would be the main seal, right? Any chance it will 'wear in'? (the crank surface had noticeable worn grooves in it where the old seal rode).

pretty bummed right now at the prospect of pulling the tranny, clutch & flywheel again...

If there was a noticeable groove on the crankshaft that's not good. No it won't wear in. I actually need to do mine and haven't seen one of these yet up close but I was hoping it might be a teflon seal but I am starting to doubt that. The answer to the worn crankshaft would be either a sleeve or place the seal into the carrier slightly deeper or shallower to avoid the groove. Easier said than done though because the seal still needs to be perfectly perpendicular, although sometimes if your lucky and this is a known issue the replacement seal is designed to ride in a different spot when installed flush.

Also I think there is sensor or something on the left side of the block that can look like a rear main leak so maybe check that.

That's a drag...It sounds like you did it right. Like you I bought just the (corteco) seal and re-used the alum housing. I focused on getting it level/even and tried to have its installed location somewhat different than the original location of the seal. Mine isn't leaking.

How soon after you started it up did it start leaking? The steady "drip" you mention has me wondering if it is something other than the rear main seal, which should be more of weep. Either way, you are probably going back in. Should be easier/quicker the second time.

I ran it for about 5 minutes on the lift and didn't see any leaks. I've since driven it about 50 miles, put it back on and saw the drip. It's not gushing but will leave about a silver-dollar sized puddle on the ground after driving.

I think I've narrowed it to the RMS because it stops dripping when parked. The only other two places I think it could come from are the passenger side lower RMS carrier bolt that goes into the sump or the seam between the RMS carrier and the block. But, I believe both of those will be below the oil level when parked, and if so, would keep leaking until the oil level drops down below either of those (meaning like a quart or two on the ground).

When you say you put the corteco seal in the carrier so that it rode on a different place on the crank, do you mean you pressed the seal in further so that it was not flush with the top (rear when mounted to the engine) of the carrier?

I'm thinking that's what I should have done. I was thinking I should buy the BMW kit with the carrier, etc., but I'd be afraid it would ride in the same spot on the crank as the original. I can't believe this problem wouldn't come up more often, though, as I've only got 117k miles, and I didn't see any signs of the rear leaking before I replaced it as PM.

Are you sure the leak is NOT from the Trans side?

Not 100%, but it seems like it's motor oil. I did replace the trans input shaft seal as well. It's a manual trans, so the fluid isn't pumped like an automatic, and I feel it's leaking too much to be from a manual trans. Also, looking at the bellhousing, it seems a leak from the trans input shaft would run pretty much straight down and out the bottom of the bellhousing, and not run over to the side first.

The leak I'm seeing looks to run to towards that big bellhousing bolt on the passenger side and then runs down the bellhousing until it hits the vertical oil pan bolt, and that's where it drops. The RMS carrier has this ledge angled in that direction, which is furthering my belief that it's either the RMS or, less likely, the carrier bolt or oil pan to RMS carrier interface all in that area.

The seal doesn't seem to be teflon. It's a very delicate double lip seal and does not have the tension spring like most seals do. In fact, in the instructions, they tell you not to touch the sealing lip at all for risk of damage.

I've seen those speedi sleeves but can't find one ready-spec'd for the M54. I think my next time in, I'll recess the new seal a bit further and give that a shot. Hate to do this trial & error though since the pain in the a$$ it is to get to.

Yes this is what I mean.. But my primary focus was getting it level/even in the carrier, and it was essentially flush with the top. I did not have a tool to get it down below the top of the carrier, and keep it level.

Thanks, I guess my big question now is should I order the full BMW kit with the seal already correctly placed in the retainer, or just go for the seal again. (I don't want the car to be down several days if I tear back into, inspect and then order parts).

On one hand, using web searches, I haven't found anyone that had a subsequent leak when using the full kit, and I can't imagine that my 117k mile motor is unique with it's light grooving on the crank. Surely, BMW would address this in TIS if were a common issue.

But, on the other hand, if somehow my situation is unique (crankshaft grooving), I don't want to 'adjust' the factory-approved kit. I guess I'm no worse off if I have to move the seal further into the retainer, though, than if I had bought just the seal.

Gotta get that order in before my fcp euro coupon expires tonight

If I were in your shoes, I would buy a new seal already installed in a new carrier. There seems to be a lot less chance of a leak that way. I would want to avoid going in a 3rd time at all costs.