Clutch hydraulic blues

[Oldtimerfahrer]

Hi all,

A few days ago, on a bridge of course, the clutch started to not disengage the motor. Even pumping only helped to get off the bridge. Flatbed home. So the hydraulics are 20 years old, I ordered all new and the E21 hose as well, since I have the O/D 5-speed box installed. Went through the pain of replacing the slave, cursed some but got it out...aired it, ok, but still no clutch. I have the master, so that is next...but are there other possible issues other than these two? I didnt see leaks, but the level in the reservoir was lower, so I assumed that one or the other was guilty. It would be depressing to replace the master and still have no joy...

Andrew

[halboyles]

Check for brake fluid puddling in the pedal box.  Also pull back the rubber bellows on the master and check for fluid there.  You can check for puddling by sticking a popsicle stick down through the carpet/insulation to see if it comes out wet.  You will have to pull the carpet back to check inside the MC itself.

Edited September 12, 2021 by halboyles

['76mintgrün'02]

26 minutes ago, Oldtimerfahrer said:

the hydraulics are 20 years old

 

The master and slave were both leaking when I bought my car.  They may have been the originals.  Here's what I found inside the master.  I don't know what causes all that gunk to form, but it'd make it difficult for the fluid to pass through those tiny holes.  I suppose you could try cleaning yours.

 

One little circlip and you are in.  Here is what I found.

As you can see, there are a bunch of little holes that can plug up.  It may just be that yours is dirty and a good cleaning will make it work again.  Especially if it is not leaking.  This one leaked before and after cleaning, but it was worth a try!

 

Tom

 

 

 

[AustrianVespaGuy]

If no leaks and pumping helps, then likely the seals inside the master cylinder are shot. I think a leak is more likely though, as there a divided section in the reservoir for the clutch so that when it leaks out, you don't lose your brakes also! The brake side of the reservoir will then look 2/3 full, but the clutch portion will be empty. Check the supply line from the reservoir to the MC, that's the most likely.

[Oldtimerfahrer]

After replacing rhe slave, In preparation for replacing the clutch master I removed the carpet and foam piece...dry as a bone. But I understand the fluid can go back instead of out on rhe master. The slave leaks outwards always...?

[Oldtimerfahrer]

14 minutes ago, '76mintgrün'02 said:

Here is what I

That's a lot of gunk. The fluid in the slave was ugly, looked like graphite colored fluid but when I bled it the fresh fluid was clean. Will pull the master tomorrow. 

[AustrianVespaGuy]

7 hours ago, Oldtimerfahrer said:

But I understand the fluid can go back instead of out on rhe master. The slave leaks outwards always...?

Master can either leak on the inside (piston seal) and come into the pedal box, OR it can leak where the supply and slave feed lines enter it on the outside and then drip straight down onto the floor.  My money is still on one of these on the outside.

[Mike Self]

All that gunk that Tom found in his clutch MC is dissolved rubber bits that settled in the lowest portion of the whole hydraulic system.  It's also one of the reasons BMW wants you to flush out your hydraulics annually.  Some people (who are not racers) actually do.  

 

I was always taught to replace both M/C and slave when one starts to leak, as the one you don't replace will then be the weak point in the system, and you'll end up replacing it anyway.  Do it all at once and be done with it.

 

mike

[Son of Marty]

If it's not hydraulic, there's only a few things that could go wrong, like a bent or broken push rod, very unlikely, broken/cracked throw out lever, happens but not all that offten, throw out bearing comming apart but that would almost surely make a bunch of noise, clutch is in fact disengagine but the pilot bearing  ceased, proabaly noisey, or the presure plate is not totaly disengaging/clutch, cover springs broken. I can't come up with any more.

[Henning]

Slave bleeder pointing down?

#7

Won't work otherwise.

 

henn

 

Edited September 13, 2021 by Henning

[Oldtimerfahrer]

Thanks to all for the input, I did plan on replacing all three items, assuming the E21 hose does the trick. When I did the conversion, I didn't have the E30 hose at hand, so I have a rubber hose from the MC to a bracket, then a hard line to the slave cylinder. In retrospective, not a great idea, the rubber should isolate the vibrations...but the hard line has not failed but I was thinking that rubber hose might be ancient. I bought the E21 318i 5-speed hose with the metal hook form on the slave end hoping its long enough. The pieces I have look like a combination of Hennings picture, probably not the right combination either...sins come back to haunt I think..

 

[Oldtimerfahrer]

4 hours ago, Henning said:

Slave bleeder pointing down?

#7

Won't work otherwise.

 

henn

 

Hi,

Bleeder is pointing down, otherwise I would not be able to bleed it..but the picture shows a hard coupling from the slave to the bracket, then a rubber hose to the MC. I purchased 21 52 1 120 306, which is a combination of rubber and metal hook end, with the hook end , so part 1 in the picture actually looks like this below.

Does bracket 4 mount to the gearbox and then pipe 1 connects the master to the hard pipe 5? My car did not have a gearbox in it, someone had sourced a 265 box and cut the old mounts but did not get any further. Now looking at it, bracket 4 should be on the gearbox... which then would all make sense to me.

Andrew

Edited September 13, 2021 by Oldtimerfahrer

[Oldtimerfahrer]

On 9/13/2021 at 5:27 AM, Son of Marty said:

If it's not hydraulic, there's only a few things that could go wrong, like a bent or broken push rod, very unlikely, broken/cracked throw out lever, happens but not all that offten, throw out bearing comming apart but that would almost surely make a bunch of noise, clutch is in fact disengagine but the pilot bearing  ceased, proabaly noisey, or the presure plate is not totaly disengaging/clutch, cover springs broken. I can't come up with any more.

Well, the rod was ok and the hydraulics are now replaced and aired out. Pedal has pressure but no action on the clutch. It does not disengage. I had no noises, so the the throw out bearing is not likely. No chattering clutch, operated well until ceased operation. Now that I think of it, I am not sure my pumping actually did anything. The spring in the bellhousing on the opposite side of the clutch slave has no movement when the clutch is depressed, even if its just a pivot point, I would have thought that it would have some movement or at least you could feel when the throwout arm moves....A bit at a loss on what to check. I dont really want to pull the whole thing unless I am sure I cant avoid it.

Andrew

[dlacey]

You can operate the clutch at the bell housing using a long metal bar....at least to prove that there's no mechanical issue with the pressure plate, release bearing or lever.... If that all checks out then bleed some more....

[Oldtimerfahrer]

44 minutes ago, dlacey said:

You can operate the clutch at the bell housing using a long metal bar....at least to prove that there's no mechanical issue with the pressure plate, release bearing or lever.... If that all checks out then bleed some more....

You mean, pull the slave and try to depress the release lever manually via the small hole?  The overdrive box 245/4 has the lever inside the bell housing unlike the 232 4-speed.

Edited September 15, 2021 by Oldtimerfahrer
grammar