Gear oil behind clutch slave cylinder - advice please

[fatnfast]

Well, finally got the new clutch hose all sorted, but as steptoe pointed out its much easier to remove the slave cylinder to refit the hose/banjo bolt, but...

Behind the slave there is a few drops of gear oil (its got that unmistakable smell). A quick serch reveals the likely culprit is the seal that sits deep in the slave cylinder cavity.
I guess it would make sence to change this before it gets worse and contaminates the clutch.
Can this be prised out without further stripping the bike?
Does the push rod pull out from here as well, as I might as well put a new felt washer on it.
Any advice on anyone who has done this before would be greatfully received

 

[Myke Rocks]

Bad news:

Well, finally got the new clutch hose all sorted, but as steptoe pointed out its much easier to remove the slave cylinder to refit the hose/banjo bolt, but...

Behind the slave there is a few drops of gear oil (its got that unmistakable smell). A quick serch reveals the likely culprit is the seal that sits deep in the slave cylinder cavity.
I guess it would make sence to change this before it gets worse and contaminates the clutch.
Can this be prised out without further stripping the bike?
Does the push rod pull out from here as well, as I might as well put a new felt washer on it.
Any advice on anyone who has done this before would be gratefully received

In their wisdom, BMW installed the seal from the inside against a lip.
When you dismantle the gearbox, it is the last component you get to.
Guess how I know!
Worse. If you do not change it, the oil percolates down the pushrod and eventually coats the clutch plate, so you end up with a slipping clutch when you open the throttle hard at circa 5000 rpm.
Myke

 

[Steptoe]

In their wisdom, BMW installed the seal from the inside against a lip.
When you dismantle the gearbox, it is the last component you get to.
Guess how I know!
Worse. If you do not change it, the oil percolates down the pushrod and eventually coats the clutch plate, so you end up with a slipping clutch when you open the throttle hard at circa 5000 rpm.
Myke

That's the 1100 gearbox you're talking about, which hasn't got a clutch slave cylinder.........

The 1150 gearbox with the hydraulic clutch and slave cylinder is a different beast altogether.

The small seal can be prised out from the rear. And the pushrod can also be removed.
Be careful what you use to remove the seal, you don't want to score the recess where the seal locates. A couple of strong picks with 90 degree ends are ideal.
And a long socket to insert the new seal. Take note how deep the old seal is seated.

 

[The Grey One]

That's the 1100 gearbox you're talking about, which hasn't got a clutch slave cylinder.........

The 1150 gearbox with the hydraulic clutch and slave cylinder is a different beast altogether.

The small seal can be prised out from the rear. And the pushrod can also be removed.
Be careful what you use to remove the seal, you don't want to score the recess where the seal locates. A couple of strong picks with 90 degree ends are ideal.
And a long socket to insert the new seal. Take note how deep the old seal is seated.

That's a relief! My 1150 is still in bits, new parts should be there by the time I get back home to Austria after Easter. I almost certain that it was clutch fluid that caused the slipping but wanted to replace the oil seal anyway. Now I can breath again, thanks Steptoe

John

 

[fatnfast]

Thanks Steptoe, that info really helped.
I have just managed to extract the seal, what a crap job that is when its still on the bike. In the end I used a couple of coat hangers bent at the end as my pullers, coupled with a large blunt screw driver. I didnt trust the little picks I had as they are pretty hard/brittle and I didnt want the end snapping off and falling into the gearbox .
I did measure the depth, so will refit it as it came off. Its a pretty deep seal thats ribbed on the outside, so I guess you could get away with minor scratches getting it out as long as they dont tear the seal when you refit it. The pushrod looked fine and no oil had got as far as the felt bush, so it looks like I caught this in time.
I wonder how many other bikes are out there with this seal slowly leaking until it dribbles down the pushrod and kills the clutch? Unless you take the slave off you cant tell. I might cut a channel in the paper gasket that fits between the slave and gearbox, a dribble spotted here could save a few quid in the long run.
Parts ordered including a new slave as I dont really want to be doing this again for a few years!

 

[<<Mark_C>>]

How dry should the area behind the slave be?

When I pulled the slave cylinder out on mine to renew the clutch hose a few weeks back I found a smidge of oil in the recess. Didn't amount to very much so I just wiped clean and re-fitted. No sign of clutch slip. I didn't bother to replace the seal. Is a bit of oil in there normal?

 

[fatnfast]

There should really be nothing behind there. The seal keeps the gearbox oil out and of course the slave cylinder itself is a sealed unit. There was not much behind mine, maybe a teaspoon full, but I have no idea if that built up over the years or is a sign of it recently failing.

It does make you wonder why BMW put a paper gasket between the slave to gearbox mount though I assume its just to stop dirt/water ingress from the road, but it does a good job of hiding potential problems.
I will be cutting a little slit at the bottom of my new gasket as an 'early warning' system.

 

[<<Mark_C>>]

Hmm... Might have to take another look then. I presume you have to withdraw the pushrod first so you can hook the seal on the inside?

 

[fatnfast]

Yes, it just pulls out, but give it a wiggle to help it. The bit of felt on it costs a couple of pounds, so Ive invested in a new one.
Take your time with the seal, it has quite a depth. Although this depth means you will proberbly get away with the odd tiny mark on its housing pulling it out it, its best avoided by being a bit careful with the screwdriver/picks.
Mine started to full to bits as I picked at it, so watch out for the little circular spring that holds the seal lip tight and be sure to get it out of harms way. Getting the bulk of the seal rubber out the way made it easier to see where I needed to prise the outer part of the seal.
Also dont go in to far with the picks/driver as just behind the seal is a sealed bearing (which is marked 'made in England' ).
I have yet to put the new seal back in (tomorrow/friday job), but made a note of how deep it needs to go prior to removal.
I originally tried to convince myself that the bit of oil was just the seal 'breathing', but there are enough cases on here where it has been responsible for trashing the clutch .

 

[fatnfast]

Job now done. The replacement seal is now brown in colour. Maybe its an upgraded version or just a change of supplier I dont know? In the pic below is also what I used to measure the original seal depth and then use to set the new seal. A spark plug socket makes a great seal driver as well

Also, I cut a small slit in the slave cylinder gasket, so any future leaks should be spotted early. You can also see my gear indicator switch covered in bathroom sealant after I stripped and cleaned it 5 years ago. Still working well.

 

[cookie]

Job now done. The replacement seal is now brown in colour. Maybe its an upgraded version or just a change of supplier I dont know?

i think brown seals are made of Viton and are supposedly more resistant to leaking.

generally vehicle seals are Nitrile and black.