Bleeding the clutch hydraulic system

Blaise · Post by **Blaise** » Tue Dec 20, 2011 1:05 am

I just bled the brakes on my car (no issues), but the clutch system was not so easy.

Any tips on bleeding the clutch system? With the bleed screw on the bottom, it seems to struggle to get the air out (edit; I found a diagram in my factory manual. It is a section cut through the slave cylinder. Though the bleed screw is on the bottom, it actually leads to the top of the back of the cylinder...so it is bleeding from the top).

D. · Post by D. » Tue Dec 20, 2011 3:27 am

I always just loosen the two nuts on the slave, back 'em off till they almost can fall off, then push on the slave toward the front of the car. You'll hear the bubbles escaping. They'll appear in the reservoir in a few seconds. Do this about ten times, voila, done. Takes five minutes.

Mike W. · Post by **Mike W.** » Tue Dec 20, 2011 10:30 pm

There's a variety of ways, but none what you would expect. I unbolt the slave, then pump the slave pushrod several times. I never open the bleeder. Forget that bleeder screw even exists. Anyway, pump the pushrod, not the pedal, a few times, then bolt it up. If you get even the tinyest bit of pedal, just pump the pedal, it'll pump up. Might take a hundred times, but it'll pump up.

Blaise · Post by **Blaise** » Wed Dec 28, 2011 2:50 am

Well, I tried Mike's technique with about 300 pedal pumps. Still no luck. Tried mighty vac and power bleeder. Still no pedal.

D. · Post by D. » Wed Dec 28, 2011 12:50 pm

Get under the car. Unbolt the slave one quarter of an inch. Push on the slave. Ten times, you'll hear the bubbles leaving.

Blaise · Post by **Blaise** » Wed Dec 28, 2011 2:37 pm

D. wrote:Get under the car. Unbolt the slave one quarter of an inch. Push on the slave. Ten times, you'll hear the bubbles leaving.

I am willing to try that, but I actually had the slave cylinder off and push the rod in completely....many times.

I am beginning to wonder if something else is wrong. The complete clutch system, transmission, pedal cluster, etc...came out of my working 1980 528i. It worked fine then. Any chance that I could have installed the clutch arm incorrectly (I sure hope not)?

I will remove the slave and put a clamp on the rod to hold it in one place...then see if my pedal is still at zero resistance. If so, then I know it is the hydraulic system. If I get a firm pedal....then I will have to conclude that the rod has nothing to press on in the bellhousing (which would suck).

Blaise · Post by **Blaise** » Wed Dec 28, 2011 7:41 pm

Does this make sense to try?

D. · Post by D. » Wed Dec 28, 2011 10:32 pm

Okay, I'm assuming the slave bleed screw is closed tightly. You don't want it open right now. Concerning the clutch arm, it's just about impossible to install backward. The little spring that holds one side of the clutch arm (that's what I'm calling it tonight) is in there, you can see the two hooks coming out of their little holes in the bell housing on the pass. side. The little plastic pivot point on the arm is correctly installed, right? I buy 'em at the dealer, had a REAL BAD EXPERIENCE with a Bavarian Autosport pivot point. Had to tear down a 533i tranny and correct some internal linkage because it jumped out of its proper place in there, when that pivot point broke for no reason. Keep us informed, this is driving me crazy, too.

Falkenberg · Post by **Falkenberg** » Thu Dec 29, 2011 5:51 am

My car has a strange problem in the clutch slave cylinder, it sometimes looses all the liquid overnight. Up to now, the '300 pedal pumps' technique after topping up the liquid has always worked. I guess because all the pipes / hoses are in upward direction, in the end, the air will go up, and the liquid will go down.

Blaise · Post by **Blaise** » Thu Dec 29, 2011 1:18 pm

Mike W. wrote:There's a variety of ways, but none what you would expect. I unbolt the slave, then pump the slave pushrod several times. I never open the bleeder. Forget that bleeder screw even exists. Anyway, pump the pushrod, not the pedal, a few times, then bolt it up. If you get even the tinyest bit of pedal, just pump the pedal, it'll pump up. Might take a hundred times, but it'll pump up.

Mike, thanks for the clarification

I had done this before pumping the pedal. I fully cycled the pushrod about 10 times.

I did not have a chance yesterday to have another go at this, but will do so in the next couple days.

Thank you all for your input. I will report back soon.

1st 5er · Post by **1st 5er** » Fri Dec 30, 2011 6:50 am

Blaise wrote:Does this make sense to try?

Yes, and thanks for posting the link.

Jeff Dennis · Post by **Jeff Dennis** » Fri Dec 30, 2011 12:33 pm

Thanks for the link.... same principal as a brake power bleeder.

Blaise · Post by **Blaise** » Fri Dec 30, 2011 10:43 pm

Well, I tried every tip that I was given, to finally discover a leaking master cylinder. I imagine that all of these methods normally work.

I will replace both cylinders.

Thanks so much for the help.

1st 5er · Post by **1st 5er** » Fri Dec 30, 2011 10:46 pm

But glad you figured it out.

I don't look forward to the day I have to replace my master.
Wasn't a lot of fun on the E28.

Blaise · Post by **Blaise** » Sat Dec 31, 2011 6:09 pm

1st 5er wrote:
But glad you figured it out.

I don't look forward to the day I have to replace my master.
Wasn't a lot of fun on the E28.

I pulled the whole system out in about 20 minutes. It should not be hard to replace on the E12

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