Rear Main Oil Seal Removal ~

I believe that folks are making more of a job out of this than is necessary. I had planned to disassemble an engine for some parts and finally got a chance to photograph the technique. Here in photographs is how I remove a rear main oil seal from the engine case of, in this case, a 1978 R100/7. Notice that the bottom lip of the seal is black from oil leaking past it and, the outside edge of the seal is even with the engine case. The seal is an original factory plastic seal correct for 1978 which has probably not been replaced before this.

First photo is the seal in place: Note oil on lip and seal position in case.

Special Tool...installed~

Give special tool a twist~

Grip tight and twist hard left or right~

Job is done. Install new rear main seal.

[QUOTE=s09rwmb;730066]Job is done. Install new rear main seal.[/QUOTE]

I hope you block the crackshaft before doing this.

[QUOTE=donbmw;730106]I hope you block the crackshaft before doing this.[/QUOTE]I did not block the crank shaft. The empty engine block and some of the parts are currently sitting in my SK machine. As illustrated there is no prying done to release the seal - its diameter is reduced and it's pulled from the pocket 'almost effortlessly' which was exactly the point of this post. Putting a new seal in or the fly wheel back on is quite another issue especially for anyone doing this job for the first and only time they are likely to need it done. Block the crank shaft as necessary....


Note that sometimes you must peal a bit of the plastic away to get to the metal core of the seal...

Very interesting. I'm pulling the main rear seal on my bike this coming weekend, as it happens. This will help a lot. Thanks for the excellent pictures.

I have changed the seal on my R90 back around 1987 and even with the BMW manual I have didnot know at that time I need to block the crack. Just got lucky that I didnot have any problems then.

Matt Parkhouse's column in current issue describes this subject.

[QUOTE=kentuvman;730251]Matt Parkhouse's column [in the Owners News] current issue describes this procedure.[/QUOTE]Nope, sorry - Matt uses a slide hammer and occasionally a punch to remove the seal. This method uses pliers.

Thanks for posting this. I'm performing the same repair on my '72 R50/5. I was wondering what the ring is that's mounted on the two pins behind the seal. I see one in your picture and I was wondering what this is and it's purpose.

Thanks!

Took my /5 apart to replace rear main seal and after inspection realized it was transmission seal that was leaking. So you might have one of those in hand just in case.

:usa

how do you block crank

you can buy a tool to thread into the frnt of the crank, or use rags or something similar between the front cover and crank. i used pieces of bicycle inner tube taped in position.