Good evening all,

I posted this in a different sub-forum, but didn't get much response. I'm re-posting here as this sub seems busier and I'd really like some input. Forgive me for the dual posting... (copied and pasted below)

Something in my clutch system died today. Clutch had been engaging with the pedal only ~1/3 off the floor (kind of spongy, but it worked okay, I guess) - today it didn't come back up. The pedal will not disengage the clutch and will not return back to normal (neutral) height. It's not flopping around and I can easily pull it up by hand, but there's not much resistance when I push it back down.

Can't find a DIY for bleeding the clutch system. Been searching the forums here but I can't find an answer to: what spring mechanism actually makes the pedal return to it's "full-up" position? I know it has a rather weak return spring on the pedal arm, but would a dead slave cylinder (alone) allow the pedal to stay on the floor? Is it the actual pressure plate springs which push back on the bearing, then the lever, then the slave, then the master, to push the pedal back up? Does the fluid actually flow backwards to accomplish this?

With the slave cylinder off the mount, should I be able to push/move the clutch throwout lever with my foot/leg (as the slave does in normal operation)? If I can't, is this a sign of a fubar'd throw-out bearing? (Haven't tried this yet, btw.)

There is some residual fluid on the plastic lower engine cover. Obviously, the slave is leaking (not from the dust boot, though). I'm planning on replacing the slave on Monday but I want to make sure that's the only problem.

I'm not replacing the master cylinder just yet - it looks fine on the outside, and no leakage inside the cabin. I'd rather not throw $75 parts at the car for no reason, but if I do change out the M/C does the fluid feed line just press onto the top of it during installation - is just a nipple?

Bleeding: as far as I can tell, the push-on tube on the side of the brake fluid reservoir (which, mine is full) is what feeds the master cylinder; then the M/C pushes fluid down the metal (and sometimes flexible) tube to the slave. I don't see a way to bleed the M/C. Do I bleed it all through the slave?

Finally, because my reservoir is still full, it's apparent that the clutch hydraulic system isn't drawing fluid from it. I'm a new owner, so I have no idea what the PO did or didn't do. Car has just over 100K on it ('06 R53).

Ultimately, if I do have to replace the clutch kit, what price range am I looking at - respectable import repair shop, non-dealership - for parts & labor (in Austin, TX)?

Any tips and suggestions are welcomed.

 

Here's a DIY on how to bleed the clutch. And here's a video DIY also. Good luck.

 

Thanks for that vid. I like his pressure bleed method, and good explanation of the system. Does anyone know if pressure bleeding like that alleviates the need for "the tool" to compress the slave piston before bleeding? I'm sure reducing the area of the slave piston travel is a good thing, but... seems awkward and not what the manufacturer/dealer service tech would recommend. (Or do they?)

 

A heads-up to other slave cylinder newbies. For those of you reading this post and swapping clutch slave cylinders for the first time, make sure you check this...

Picked up the slave this morning. Installed it easily enough. Then it started pissing fluid out the feed tube connection while I was pressure bleeding it.

From the few DIYs I read about slave cylinder R&R, nobody mentioned that there's a rubber nipple/seal that should be on the tip of the metal feed line. There's a plastic cone on the line that fits into the slave hole (what you clip the wire bale through), but since I didn't know to look for it, the nipple was left out of the connection - the new slave didn't come with it, and without it there will be no pressure seal.

I found the seal in my old slave cylinder and picked it out carefully with a pick tool. Pushed it onto the end of the metal feed tube and voila' - seal!

Sadly, the slave isn't my only problem so I'm getting a master cylinder this afternoon. Looks pretty easy to install as well. I'll report back on my success or failures.

By the way, does anyone know the trick of getting the mesh screen out of the brake fluid reservoir opening? Just spins and spins and doesn't seem to want to pull out.

 

Yes you need some sort of tool either the BMW sst or a home made one. You need to compress the slave completely and leave it compressed while bleeding it with the pressure bleeder.

 

That screen snaps into a slot in the reservoir housing and I used a very small screwdriver to lift one edge out of the slot so I could flex the screen and pull it out.

Eric

 

Makes sense. Thanks.

 

Okay, not to be jerky, but can you (or anyone) explain why the tool? Evacuating the air is the point, and I believe that pressure bleeding would take care of that. I can see how compressing the slave cylinder, then bleeding the air out and releasing the cylinder would draw in more fluid from the feed line. But I don't see why a compressed cylinder would pressure-bleed better than a non-compressed one. Was the tool an afterthought by Mini to fix a lousy bleeding issue with the slave?

Further, I installed a new master as well as the slave. Bled them (pressure, no "tool"). Bubbles came up through the fluid reservoir nipple and the system took a good amount of fluid. Still no back pressure at the pedal. It was going up and down with very little effort, then something popped underneath the car on the tenth or so pump/stroke. It happened at the bottom of that stroke, then pedal stayed down. Got under the front of the car to see that the metal feed line had blown out of the slave cylinder - from what seemed like a very little amount of pressure. (yes, it was installed and clipped in properly)

I have the sinking feeling that the throwout bearing is fubar'd and the clutch lever is jammed where it is, meaning that the slave piston couldn't even move it.

If any of you think that using the bleeder tool trick would change any of these symptoms, I'll rig something up and try bleeding again before I have to tow it to a shop for a clutch.

Thanks for all of the responses so far. This online community is pretty great.

 

Bump and an update...

Installed both slave and master cylinders, but still didn't have clutch. Fearing that the throwout bearing had grenaded, I had the Mini towed to a reputable shop. They took a look at the slave cylinder, re-installed it, and bam! - clutch is working. Good news, when I had been planning on paying for a new clutch. The culprit? See my heads-up below:
Even after I figured this out, it seems I still didn't get the damn seal installed correctly. It looked like the thing is supposed to slip over the end of the metal feed tube (below the plastic V-shaped retainer) and then fit into a recess in the bottom of the slave hole. Maybe pulling the line out after I installed it buggered up that seal. Anyway, the shop took it apart and did it right. I'm picking it up later today. You can't imagine how happy this makes me! Live and learn...

 

When the slave is uncompressed it leaves a space behind the slave's piston. When the slave is bled the fluid comes in and right out the bleed screw. Any air or old fluid in the space behind the piston gets left inside the slave. When the slave in compressed this space is almost non existent allowing for a complete bleed of the system.

After bleeding it is sometimes necessary to just pump the peddle quite a few times to get full pressure.

The master cylinder may have air trapped in it too. These can be a pain to bleed. Bench bleeding is a good idea before installing it. It helps a lot.

Aside from that you should have some one help you verify the slave is extending. One person pump while the other watches the slave.

Typically if the TB cam off the fork or came apart you should be able to move the arm on the side of the trans by hand.

If it is stuck you probably wouldn't be able to get the peddle to compress that well.

 

In theory, fluid would come in the feeder hole, fill the cavity (no matter how large) from the effects of gravity, pushing air out the bleeder valve until only fluid is left in the cavity behind the piston. I would also think that holding the slave as vertical as possible with the bleeder up, even tapping it while it fills, would help. Making that cavity as small as possible (by compressing the piston) would certainly help in all cases of bleeding any cylinder.

Not arguing with you at all (nor anyone who states the tool is a necessity). Your description makes sense except for the part about the fluid running right out the bleeder hole before filling the cylinder cavity, and I'm not arguing otherwise - if it does, it does. I just didn't see how using the tool was imperative unless there was something odd inside the cylinder. Ergo, it must be a design flaw.

 

OK, tried bleeding my slave cylinder this way (including the "clamp"), BUT: after a few pushes on the pedal, nothing comes out - no fluid or air - and the pedal goes to the floor w/ no resistance and stays there...

?????

fwiw, I'm wrapping up a flywheel/clutch/pp/bearing change - the release bearing had "grenaded" (thus allowing extended travel of the slave cyl. piston). Related?

'02 MCS, 86k

 

so i just added a manual trans to my car in place of the cvt and im having trouble bleeding the clutch. everything is hooked up and i have a power bleeder hooked up to the slave cylinder. the trans arm for the throwout bearing is pushed up keeping the slave as small as possible and i have been pumping the clutch pedal with no luck. you can hear the air and fluid cycle back and forth in the master cylinder reservoir but the level is not going down and nothing is coming into the bleeder bottle....

any suggestions?

 

Did you sort this out?