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j_hurricane_y 10-01-2008 05:47 PM

Can we compile definitive clutch slave cylinder fix thread?
I'm hoping by starting this thread that those who've had the dreaded clutch slave cylinder failure can share their experience by linking to past posts, sharing photos taken, and detailing solutions, both tried-and-failed and tried-and-true. I myself have recently had a slave cylinder failure. My first indication was not a performance shortfall of the clutch (which others have had -- see, but upon changing the fluid, I noted the distinctive smell of 90W gear oil. While I only have a little over 7000 miles on my second-hand '03 (manf. in 09/02) BCR, the bike has been unridden for long periods of time. I am not sure at this point if that is a contributing factor or not.

Another symptom is that upon emptying the clutch reservoir I discovered rust colored sediment at the bottom. Unfortunately, I only have a shot after I emptied it due to camera/computer issues. Because this sediment was heavier than the DOT 4, it sunk to the bottom so when I first took off the cover, everything appeared to be fine. That is, it looked honey colored although I was admittedly operating in low light. Actually on second thought, the fluid that I bled off initially from the bleed valve (by the rear shock) was pinkish in color so I should've realized at that point something wasn't quite right. I admittedly lack a lot of experience in twisting wrenches on a boxer, but I try to make up for that by not being afraid to try. Anyway, here's the shot of the sediment.

When you see something suspicious like this, the next step is to trace it to its source. In this case, that's the slave cylinder which is located underneath the air box, in front of the swing arm / shock. Fortunately, you do not have to unbolt the rear subframe as the service manual indicates. You *only* have to remove the rear wheel and remove the rear shock. Be sure to support the Paralever. With the removal of three allen bolts, the slave cylinder comes out by tiltling it up at the rear to clear the "cross beam." See page two of "jweicht's" thread for pics or below for how mine looked (not good).

Another thread that I found interesting was this one where a couple folks talk about drilling a weep hole. I don't quite know where specifically that weep hole should go or what specific symptoms indicate it is necessary. Don't bother reading to the end btw ... no conclusion to the original problem other than "it went away."

More below and for those of you with more experience in this forum and/or with this problem specifically, can you please offer additional links and/or advice?

AntonLargiader 10-01-2008 06:02 PM


Originally Posted by j_hurricane_y (Post 4213565)
For those of you with more experience in this forum and/or with the problem, can you please offer additional links and/or advice?

Sure: take the picture BEFORE you remove all the fluid.

wswartzwel 10-01-2008 06:13 PM

My 02 came with Honey flavored fluid that I change every year... You got the model with the butterscotch fluid. :)

That color could be from moisture. Only way to tell anything is to pull the slave and inspect.

j_hurricane_y 10-02-2008 08:17 AM

I detailed in the other thread that I was not able download my pics off my camera; therefore the pic I posted was taken with a different camera and is as you noted, after the fact. It still shows that the fluid is discolored. Furthermore, with the reservoir full, the discoloration was not apparent so not much point in posting that pic even if I had it. I have to say Anton, that for a thread that was created with the intent of helping others out, your reply was definitely contrary.

Bill, the reservoir and removed fluid (not yet thrown away) definitely smells like gear oil so I think it is more than just a little moisture affecting the color. As you point out, the only way to know is to pull the slave cylinder which I plan on doing tonight.

I don't plan on detailing my findings further unless I discover something new. My point in creating the thread was for others to detail their experiences so that all the info is consolidated on one thread. Maybe that was a misguided effort and this thread will die a quick death.

AntonLargiader 10-02-2008 09:34 AM

I didn't mean to be contrary. If you want this discussion to be about creating the definitive slave cylinder thread, you need to give more information for future readers. Pics of good fluid, pics of bad fluid, etc.

Sounds like you're just starting a 'my slave cylinder is bad' thread rather than what you suggest in the title.

j_hurricane_y 10-02-2008 04:32 PM

Anton, w/o getting into a pissing contest, what you suggest is exactly what I thought I was asking the members of this forum compile. I quote, "For those of you with more experience in this forum and/or with the problem, can you please offer additional links and/or advice?" I'm a first time BMW owner with this BCR and the learning curve has been a bit steep. I don't have the experience to share on my own, but I reckon I'm gaining it in fairly short order. That said, your point is well taken in that I started off the thread detailing my problem and only later in the post suggested it become something more than just about me. I think I will edit it to remove the extraneous details and provide what I've learned so far.

j_hurricane_y 10-02-2008 05:51 PM

Pics of ugly slave cylinder
Here's what my slave cylinder looked like. The rust colored sediment seen in the reservoir is a clumpy, greasy, clay-like mess in the "housing" (I don't know the proper name) where the cylinder contacts the clutch push rod. I believe it to be very similar to what jweicht's afforementioned post details.

This is the end of the cylinder with the throw out bearing in center (right?). Ugly yes?

Here's an admittedly shoddy pic (hard to get a good shot b/c of its location) of the clutch push rod and housing. It too is full of the rust colored gunk.

I believe the next thing to check is if clutch (DOT4) fluid got in the gear box. I do not have a 14mm allen (I believe that is what it takes) to pull the gearbox drain plug, but I did open the fill plug. In my case, the gearbox was apparently over filled because I got quite a bit of gear oil out. What I did get out was a gloriously golden color and did not appear to be contaminated. I believe if there was clutch fluid in it that it would float on top so I think I have very similar symptoms to jweicht. I will get the proper tool and completely drain it to double check.

Any suggestions on how to clean the push rod housing? A tiny spoon perhaps?

wswartzwel 10-02-2008 06:42 PM


AntonLargiader 10-03-2008 04:16 AM

One of the problems is that the seals are not compatible with the 'other' fluids. I think this is why BMW went to mineral oil on the R1200 clutches; it is not incompatible with gear oil.

This is what happens when DOT4 slave cylinder seals are exposed to mineral oil. Gear oil would be similar:

The rear surface of the input shaft (where the rear input seal rides) gets trashed when these seals go. I'll take pictures of a bad one at some point.

Basically, if you get a reservoir full of mud, you have a bad slave cylinder and you might need to replace the rear input seal. Fortunately that can be done without opening the tranny, but if the shaft surface is damaged it's very awkward to smooth that out in place.

j_hurricane_y 10-03-2008 05:51 AM

Wow! What a excellent repository of information you've compiled on your website. Thank you for sharing that! You are the man.

Initially I posted a question here, but figured it out with the service manual. Answer is that yes, it is a dry clutch (automotive style) but DUH!, the gearbox is between it and the slave cylinder. Still, I suppose it is possible for the DOT4 to travel down the clutch push rod to the clutch???

roger albert 10-03-2008 08:10 AM

> Still, I suppose it is possible for the DOT4 to travel down the clutch push rod to the clutch???

Yes, it is, unfortunately. Not as rare of an event as one would like on oilheads.
BMW has went back and forth with Felt seals, rubber, and none on the pushrod, so they seem to be struggling with a definitive answer/solution too. And on some of the oilheads, the little seal (only replaceable from the inside - grrrr) on the end of the input shaft goes, and lets gearoil down the pushrod. I think the last R12GS I worked on had that problem. And its pushrod had NO felt bit or anything else to slow/minimize contamination. Very annoying.

j_hurricane_y 10-03-2008 09:11 AM

Thanks Roger. I got less details but the same basic story from a tech at Bob's BMW; great customer service over the phone btw. Informed me my next step should be to start working my way through the various seals to verify how far the DOT4 got. Sounds like the two week upgrade/repair project I had in mind for my bike has now become a winter long project. Time to start reading up on how to pull the gear box ... good times.

repoe3 10-03-2008 11:05 AM

sorry to hear about your woes...
this thread may be of some help in removing the tranny:


j_hurricane_y 10-03-2008 12:05 PM

OMG! Why is that not a Sticky?!! Glorious post man. That settles it. I'm tearing her apart; shoot, I'm nearly halfway there already. Might as well yank the gear box and check the splines ... maybe send the shaft off to get it coated as well. I'll have to inquire with Moybin if he's torn it back apart to take a look.

Repoe3, note I too am in the VA-DC area. Want to come over this weekend and help me tear apart a motorcycle? :) I've got a Giant just down the street that I'm certain must stock your favorite beer. I joke ... with your post, I think I'll be good to go!

RBMann 10-03-2008 12:11 PM

I can't find the post about drilling a drain hole in the trans. cavity that the slave cylinder goes into. This seems like a good idea, while you are there. Fluid can drain out and let you know before it becomes a bigger problem.

Sorry I can't find the post with photos.


wswartzwel 10-03-2008 01:37 PM

Page 2 of the thread is the picture of Essings Bike with the weep hole... That bike now belongs to GaryK

Try using "both hands" when looking for things next time RB.... :D

RBMann 10-03-2008 02:07 PM


Originally Posted by wswartzwel (Post 4217190)

Page 2 of the thread is the picture of Essings Bike with the weep hole... That bike now belongs to GaryK

Try using "both hands" when looking for things next time RB.... :D


Thanks! I think?

I am trying to cut back on my meds. and it is not working so well.

WARNING! Do not drive or operate heavy equipment. Do computers count?


wswartzwel 10-03-2008 02:17 PM


j_hurricane_y 10-03-2008 04:29 PM

You guys are awesome. Thanks for digging up the link Bill. I've got the rear subframe off now and have drained the 90W to take a look. I'm going to move my step by step progress back over the the "Am I a masochist..." thread and will update this thread with pertinent "lesson's learned." Anyone else who has gone through the failure and repair of the clutch slave cylinder / gear oil in the clutch fluid problem, please post your experience here. Links to past threads are so helpful as the search engine is a bit cumbersome and the volume of posts you get with this topic is fat. I did find this thread with some more details about initial symptoms and a photo of a seemingly good looking slave cylinder (compared to mine) that also had issues; thought it worthy to include here -->

ckcarr 10-03-2008 06:48 PM


Originally Posted by j_hurricane_y (Post 4216969)
OMG! Why is that not a Sticky?!! Glorious post man.

Eventually the truth will be revealed to the inner sanctum. Stickies are for whooses...

Do you think you can simply stroll into the Pelican and turn a page of a book for all to be revealed...

The knowledge you need is here grasshopper....

Yopu have actually attracted the three wise men of the board...

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