Leak around rear main seal

[fast330i]

So here we go again, since I got this car I wasn’t able to drive it a week straight

Where I live not many greats mechanics or shops.

Here was my last post: https://www.bimmerpost.com/forums/sh...php?p=31515164

The service changed yesterday: the rear main seal, torque converter seal and a revision + oil on transmission.

The service was a BMW Authorized service one of the best in the city.

I saw a leak in the morning so I went to my friends shop to see the leak. It’s still leaking around there and I don’t know what’s the cause….

I’ll attach some images below let me know if anyone encountered or had similar issues and what they changed.

I’m lost pretty much not great mechanics around me, every service (5 services) told me it was the rear main seal, but after the change stil leaking.

One option left is to go to BMW itself and have it checked there at least to have input from them. I got the appointment from them for next Friday.

Monday morning I’ll have the appointment where they changed the rear main seal.

[B58 parts]

The seal is very difficult to remove without damaging anything. And difficult to install without damaging the seal. They may not have used the correct tools and ripped the seal. This happened to me, the installation tool was not used and a few days later the bolts there were quite oily. Or they may have damaged the rear cover. Or worst case, as I also later did myself, they may have damaged the crankshaft. Sometimes you learn by destroying. The crank has to be perfectly round and clean or it will rip the seal. It's a really thin lip of PTFE and it has to be perfectly round. It's amazing it actually works and all, 7k RPM a metal snout spinning inside a piece of rubber and oil doesn't get out.

This is one area where you really want to buy the special tools. And for the love of God use the center punch before you start the drill bit. Try to pick it out first.

[fast330i]

Originally Posted by B58 parts

The seal is very difficult to remove without damaging anything. And difficult to install without damaging the seal. They may not have used the correct tools and ripped the seal. This happened to me, the installation tool was not used and a few days later the bolts there were quite oily. Or they may have damaged the rear cover. Or worst case, as I also later did myself, they may have damaged the crankshaft. Sometimes you learn by destroying. The crank has to be perfectly round and clean or it will rip the seal. It's a really thin lip of PTFE and it has to be perfectly round. It's amazing it actually works and all, 7k RPM a metal snout spinning inside a piece of rubber and oil doesn't get out.

This is one area where you really want to buy the special tools. And for the love of God use the center punch before you start the drill bit. Try to pick it out first.

Thank you for the information this is way above my expertise)) I’ll let them know Monday if they’ve done like you’ve suggested. The funny thing they are the best M car mechanics in the city. So my guess is the leak was from somewhere else and not the rear main seal? Any chance it could be other parts? Parts that often fail?

[RockCrusher]

Have had several cars with a leaky rear main seal. (Boxster and 996 Turbo.)

What I learned was first that the seal is the source of the leak needs to be clearly established.

That is a leak higher up/forward of the rear main seal needs to be checked for.

A non residual cleaner (brake cleaner in an aerosol can) is used to rinse away any grime. In some cases the tech will add a special florescent dye to the oil which lights up/glows when subjected to a black light.

Then the car is driven normally for a bit. The tech will then shine a black light around to see where any glow is which then lets him know where the leak is. 'course, with the rear main seal it can't be checked for leak sign directly.

But with both of my cars it was only after the tech confirmed that there was no leak above/forward of the rear main seal that the removal of the transmission was justified to then locate the leak source. In both my Boxster and Turbo the rear main seal was the only leak source.

I will add in the case of both cars a visual check found no leak sign at all so the tech didn't need to clean the engine and resort to using an oil compatible florescent dye.

When it was clear the rear main seal was the source of the leak the old seal was removed. I was not present for this but I'm sure the tech used considerable care in removing the seal to avoid damaging the seal bore and the crank journal. (As an ex-journeyman machinist and amateur engine builder I have some experience with seal R&R. But I didn't try to tell the tech what to do.)

Likewise the installation of the new seal was done using proper technique/tools to get the new seal installed.

One important consideration is the new seal doesn't want to be installed at the exact same position as the old seal. The odds are the old seal has worn a bit of a depression into the crank journal and the new seal won't seal properly if it ends up with its seal at this depression.

I had a new rear main seal installed in my Boxster at around 25K miles (and covered by warranty). Drove the car to 317K miles and the new rear main seal and original front main seal remained oil tight.

With my 996 Turbo the rear main seal was replaced at 110K miles (out of warranty). I drove the car to 161K miles and the new rear and original front main seal remained oil tight.

Have included 3 pics to show you what I saw with the RMS leaks from my cars.

First pic shows the spot of oil on the garage floor from what proved to be the Boxster's rear main seal.

Second pic shows the rear of the Turbo engine and the leaking RMS. Note there are other possible leak sources and the tech told me he couldn't eliminate them until he had the transmission out.

The third pic shows the rear of the Boxster engine and other possible leak sources.

'course the BMW engine doesn't have the two engine cases bolted together nor the intermediate shaft end plate which can be a leak source.