Author Topic: Rear Main Problemo (Read 3981 times)

dvmotorsports · « **on:** July 17, 2008, 05:31:12 PM »

So I fired my rebuild two weeks ago as stated in a previous thread. Wouldn't ya know it, the rear main is leaking. So yesterday I pulled everything and reinstalled it (only had 40mi on it). But this time I used some permatex Super Grey. Everything is torqued to spec. And that little fucker still leaks. And it's not a little leak. After a total of 80miles (40 on the first install and 40 on the second install) it still dumps.

Any suggestions?

bimmerfahrer · « **Reply #1 on:** July 17, 2008, 07:42:02 PM »

Two questions:
1) did you use an OEM BMW Rear Main Seal? When I rebuilt my M20 I bought one of those top end and bottom end gasket kits (Can't recall the Mfg) and went through two rear seals. Finally I sourced on from BMW and the seal itself was deeper, making a much better seal

2) Did you grease the v groove on the seal? While Bentley and other manuals say to oil the seal, I've had a few BMW mechanics tell me to use grease.

Good Luck! Hopefully this will save you removing and re-installing the transmission as many times as I did trying to solve my leak issue.

bimmerfahrer

dvmotorsports · « **Reply #2 on:** July 17, 2008, 09:37:22 PM »

Yeah. All the parts are OEM. No third party stuff except the cams (which are OE regrinds anyway).

When you say V-groove, might you have a pic?

Thanks

christophbmw · « **Reply #3 on:** July 17, 2008, 09:59:55 PM »

did you replace the crankshaft main bearings? i had the same problem, went through 3 seals!!! pain in the ASS, anyways turned out to be my bearings, they where slightly out of spec, but the crank seal didnt like it so it leaked. What happens is the crank rides on the lower part of the seal causing it to leak.....no matter how new it is. Something you might want to consider

.

dvmotorsports · « **Reply #4 on:** July 17, 2008, 10:13:21 PM »

Nope. Didn't change that. I had thought it might be the culprit. But before the rebuild it didn't leak from there at all. So I didn't bother with it. I wonder why it would start pouring all of the sudden. Arrgghh! I didn't want to do this job again.

I think I am going to put it on a lift, yank the tranny, hold the starter in place and fire it. Only problem is that the F/W would still be in the way.

Would there be another way to start the motor without the F/W? I know that sounds retarded. And I don't think there is a way. But hey, who knows.

dvmotorsports · « **Reply #5 on:** July 18, 2008, 04:51:54 PM »

Do I have to yank the crank to do the main bearings?

Also, I inspected the RMS today and I know this much. It is not leaking from the cover. It is leaking in the middle where the actual seal is.

nickmpower · « **Reply #6 on:** December 18, 2009, 11:21:49 PM »

hey did you ever solve this? I have all new bearings and it still does it. I think it might be the lightweight flywheel. I just ignore because its a very small leak. I have never seen it drip on to the ground.

btw, how in the hell did you "rebuild" your engine without replacing the bearings?

dvmotorsports · « **Reply #7 on:** December 18, 2009, 11:57:36 PM »

Everything was replaced. I was just tired of all that shit and confused myself. Anyhow, yeah I fixed the leak. There are little grooves on the flange. My rms was out of the groove just a hair in one section.