Rear main seal help

[sersnail]

Hi guys,

New member but having searched the forum, I've not seen anything of this sort yet.

Long story short, I recently replaced my rear main seal in my r1100s (preemptive strike while I was changing the clutch pack out) and about 300 or so miles after replacing it, it starts leaking again. When I opened it up again to see my idiotness, I see the seal is inverted on the shaft, as in the sealing membrane is pointing the opposite direction from instillation and opposite to how BMW says it's supposed to be.

What could I have possibly done wrong to cause the seal to invert? Is there excessive pressure in the engine? Bent seal? And what can I do to prevent me from having to spend another weekend tearing it apart again after replacing it again.

Thanks in advanced for any help.

[wswartzwel]

You have to use a special tool to push the lip of the seal toward the engine when installing. There are two seals. an inner one and an outer one with a space between them.

[sersnail]

I've looked everywhere for the tool but couldn't find it.
Could you point me in the direction of how to purchase it or could I buy it off of somebody?

I ended up using directions found in this forum along with the haynes manual to install it without the tool.

Thanks again.

[brentw1]

I use a cut aluminum coke can it is about the perfect diameter
you will need 2
use the bottom of one to invert it then slide it over the other one then the cut end is
a perfect fit over the crank, you can slit it to make it smaller but no need really
also it looks like you didnt leave a space between them.
normally if I remember correctly the inner one sets fully into the block against the machined
flange
the outer larger one is just flush with the face of the block it looks like you pressed it in to far.
I use a large pipe coupler to drive it, I forget which size but is is a stock part that I sanded one
end flat on.
or you can order the tools from bmw.

[wswartzwel]

You can take a tapered plastic yogurt cup and carefully cut the bottom out at the point where it just fits the outside of the crankshaft. oil the seal and slide the seal on from where the bottom of the cup used to be so the lip of the seal is bent inward towards the engine. then slide it over the crank and press the seal into the block

[wswartzwel]

Ha.. Brent is quicker on the trigger than me.

[brentw1]

also you can run the motor without the transmission in place to check for leaks.
just be careful to not let the throttle bodies suck up any debris

[wswartzwel]

Originally Posted by brentw1

also you can run the motor without the transmission in place to check for leaks.
just be careful to not let the throttle bodies suck up any debris

Great tip Brent!

[brentw1]

yea brent is under employed and I have about 6 bikes to get ready to flog this summer.

[sersnail]

Thanks for everybody's responses.!

For the install I ended up putting the seal around a plastic water bottle that fit snugly around the shaft, then tapped it in with the old seal. I seeded it in until it bottomed out onto the second seal, perhaps that was a mistake. How deep is it supposed to be? Is 3mm correct?

I never thought of running the engine without the transmission installed but I'll give that a try.

I'm still looking for that factory tool though.

[Jozef Schumann]

Originally Posted by brentw1

yea brent is under employed and I have about 6 bikes to get ready to flog this summer.

Great info you two. Threadjack alert:

I can help with your quest, brent. Make me up a couple of those oh-so-cool sta-in-tune DB killers I saw on your bike in a post somewhere.

J.S.

[wswartzwel]

Originally Posted by sersnail

Thanks for everybody's responses.!

For the install I ended up putting the seal around a plastic water bottle that fit snugly around the shaft, then tapped it in with the old seal. I seeded it in until it bottomed out onto the second seal, perhaps that was a mistake. How deep is it supposed to be? Is 3mm correct?

I never thought of running the engine without the transmission installed but I'll give that a try.

I'm still looking for that factory tool though.

There has to be an air gap between the two seals. That is where the crankcase ventilation port is. Inner seal all the way in… outer seal flush with outer surface.

[wswartzwel]

if you follow the arrows you can see the ventilation system goes through the crankshaft, between the two seals then out the fitting to the vent hose that connects to the air box. If the seal is covering the hole in the block, you will likely blow another seal out, maybe the front one.

[sersnail]

Because of the one failure, would it be a smart move to replace both seals now?
Just to confirm, the rear seal is seated all the way to the engine case and the front seal is flush with the outer rim.

This has been very helpful information.

[wswartzwel]

Yes, replace them both.

I can not remember if there is a a stop for the inner seal or if it is possible to push it in too far and have it rub against the bearing journal… when you get them out you should be able to see. the outer one is flush against the outer surface.

[RBMann]

I looked at a photo and it appears there is a step in the engine case that the inner seal gets pressed against to set the depth. The outer seal should be flush with the engine case. Getting the lip of the outer seal facing inward and over the crank is the only hard part. Here are some pics you might find useful.

[RBMann]

Oops, one more showing a properly installed seal.

[sersnail]

I won't have time to work on it until next week but I'll take this advice and let you all know how it goes.

Thanks for everybody's help!