Clutch

[Andre Pollard]

Had a clutch slave cylinder leak, so I changed it for a new one. Symptoms were the pedal going to the floor and staying there, and of course fluid coming out when I pulled the slave. This is the second time I’ve done changed the cylinder, and the first went smoothly. However, this time it leaked a lot of the fluid out of the reservoir and got air in the hoses / pipes / master.

 

So, I replaced the slave, bleed it via gravity until it ran clear fluid with no bubbles (with the slave removed and bleed pointing up). Then pressure bleed from the reservoir like I did before. Pedal was mushy, didn’t disengage clutch, and didn’t return by itself. I figured more air in it, so I pressure bled the system in reverse, pushing fluid through the bleed and pulling it out of the reservoir. I did this until I saw no bubbles coming out in the reservoir. I then pushed and extra 12 oz of fluid to be sure.

 

Pedal is still going to the floor. I also tried the usual method of pump pedal and basically get no fluid out when I do that.

 

Is it possible for the master to have gone bad and not build pressure but not leak fluid? Or am I missing something?

 

Thanks-

Andre

 

 

[Gary Derian]

You need a good flow to get it out.  A pressure bleeder on the master will work. Or bleed it backwards.  Air in the downward flowing tubes sticks there as the fluid passes around it.   Connect the pressure bleeder hose to the slave bleeder, or connect the slave bleeder to the left front brake bleeder and pump the brakes.

Gary Derian

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[chrich...@yahoo.com]

A pressure bleeder will do it, but you have to know that the fluid comes from a small portion of the master cylinder separated by a divider at the back. It’s easy to deplete the fluid available in this section and push air into the system again. I reduce the pressure to 7 psig and go slowly, keeping the master reservoir at maximum. With full pressure, the air can break through suddenly.

 

I haven’t done the M5 in a while, but the E90 does exactly the same thing, CDV or not. It’s because of the loop in the tubing to the slave, also.

To view this discussion on the web visit https://groups.google.com/d/msgid/bmw-e34-m5/CAOTtLQY9J7oY3Rdf0de2NV3h9XrhMP%2Bp0pcO07CqvDNJtPA_Cg%40mail.gmail.com.

[Andre Pollard]

Apparently my pressure bleeder wouldn’t flow enough even in reverse flow (pushing fluid in slave bleeder). However, Gary’s trick worked perfect and I’m now back with a firm clutch. 

Thanks 

On Jun 26, 2023, at 11:22 PM, chrich...@yahoo.com wrote:



A pressure bleeder will do it, but you have to know that the fluid comes from a small portion of the master cylinder separated by a divider at the back. It’s easy to deplete the fluid available in this section and push air into the system again. 

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