I just installed new main seal as part of clutch replacement on 1990 Z32 AT/MT. It's leaking oil like a sieve . Haven't pulled out the gear box to see it yet, but in the mean time, does anyone have any tips on getting it done right, or what I may have done wrong? I was very careful with the install, but obviously I missed seomthing. One Youtube video I watched they inserted a fine screw driver just to make sure the inner part of the seal was nicely seated around the crankshaft. Maybe even a skinny feeler gauge. I can only think that would be the problem, even though it looked fine when I installed it. I put plenty of sealant on/around the sump seal.
Rear mains are always a pain. For a start, Its never a good idea to do this job without droping the sump. By doing so you can easily remove and re-install the seal plate. I think I may have watched the same youTube video as you refer to. If you followed this guys advise then you have most likely damaged the seal. His video and instructions are not the right way to go about this job. For a start the surface of the crank should be cleaned with something like 1000 grit wet and dry. Then wiped down and lubricated with engine oil and the surface of the seal also lubricrated. With the sump dropped, the seal can be worked onto the crank without poking and damaging the seal.
Thanks for sharing your experience. Now that I have the tranny out, I can confirm that seal was definitely installed properly with no bent lip etc. I checked that video, and the guy didn't use a screw driver, but a flat rounded head seal insertion tool to make sure that lip was seated correctly as he installed it. With a bit of oil for lub, I really had no problem carefully getting the seal on without using any tool, which BTW I did AFTER installing the carrier with the sump seal. Getting the carrier on with new plump sump seal was a bit tricky, but used vice grip to pull it down to get onto the dowels. I did notice when I installed it that the outer edge was not hugging the journal, but it is the inside lip that does the sealing, so ought to be ok? I couldn't see anything wrong with the install to cause that. Before removing it, I inserted and ran a (fine) feeler gauge around and it felt all fine. I did also clean the journal seal surface with synthetic steel wool, as I saw on another youtube. I had a set of 4 grades = 1 /0 / 000 /0000, so I gently used all of them in succession. As per photo, there are some scratchs, which maybe I did with the SSS, but can't be sure. These scratches were actually not visible to my naked eye, but show up well on the camera with a flash. At the time I didn't think twice about using that SSS, as I figured the journal surface would be super hard, like internal rank journals. That said, I am surprised to see that there is a groove from the old seal (which BTW I hadn't noticed when I installed the new seal). That journal surface can't be that hard if a rubber seal can cut a goove into it - although apparently this is perfectly normal. The new seal has a much wider lip so should sit lower/on the engine side of that and take it out of play as a problem. I can't/couldn't feel any roughness/burr around that groove. So it looks like my way forward is to get the emery paper onto it and see if I can get those scratches out. A buddy (fanatic vintage car and motor bike restorer) suggested I should even get the metal polish onto it - eg Josco green, but from my on-line research, it looks like you don't want it to be TOO smooth. Could it be that some remnant micro scratching helps to provide a home for some oil to lubricate the seal??
Or else further alternative is to use a speedi sleeve. Should I go with that to avoid the risk of another failure and having to pull the gearbox out again?
ok - so after using 1500 grit emery with WD40 as lubricant, it now looks like this : Campared to previous : It looks like night and day, so hopefully that should be good now..... although doubt still lingers as to whether I should go with a speedi sleeve and eliminate the risk that there is still problem?
If you can run your nail across the wear and feel it then you aren't going to be able to polish thato out. However 9/10 times the leak isn't from the rear main seal itself but rather the lower sump retainer gasket. Just about every one I've done (a lot in the last 15 years) has some degree of wear on the crank like yours pictured which isn't a big deal at all. I like to use the old seal as a guide to to make sure the new one is seated into the housing properly. If the inner housing of the aluminium retainer has been damaged from a screwdriver or tool when removing the seal it will leak and can be fixed with a layer of gasket sealant on the seal or housing when installing a new seal. One trick is making you get the inner lip of the sleeve to seat properly and not fold over itself which it sounds like you were able to do, so I'm going to guess your problem is either the housing or the sump gasket. I've never had to use vice grips to get the housing to seat, it should be able to be worked on fairly easily - possible the seal has been damaged or disrupted the first time? Putting a bead of gasket maker on the outside will do nothing to stop a leak, oil always finds a way... but a layer of sealant on both sides of the retainer definitely can help to make the seating process easier.
Make it, i really wouldnt be too bothered with the fine lines in the crank youre seeing. As mentioned above if you can pickup a scratch on your finger nail then yeah give it a tickle with emery but if you cant then its not an issue. micro polishing the surface isnt required. If you believe the oil to be bypassing the sealing lips i would look back at the seal and make sure the coiled tension spring internally on the seal hasnt come out. Wouldnt be the first time ive come across a seal thats lost the spring or its not seated correctly which will apply unequal pressure on the inner lip against the crank. Your install looked ok from the photos, doesnt look like youve belted the edge of the seal and deformed it. Try a new seal, smear a little sealant around the outer edge, just a tickle, to make sure its not the allow carrier thats leaking, and if you want dont punch the seal all the way home, have it a couple thou off seated so the lips are running on virgin metal. For shits an giggles also, once complete and sealants dry, run the engine without the box on and see if youre getting a leak from somewhere else.
Looking at the pictures you've posted, it looks like the seal isn't even coming into contact with the surface of the crank around the bottom. If that's the case, then no wonder it leaks oil. Was the correct seal fitted? The crank surface should have uniform contact and small amount of displacement of the seal all the way around the crank. If not, its going to leak.
