Clutch not engaging

[williamlamb]

At wits end, 2004 Z4, sat dormant for 3 yrs before acquired yet did crank and drive, did hydrolic fluid change and bled brakes then clutch however due to accessibility issues screwed up and let all fluid bleed out of slave, have not gotten clutch operational since
Thus far have replaced fluid line from clutch master to resivore as well as both masters cylinders and slave, using pressure bleeder, repaired all the fluid leaks and will now stay pressurized
Proble is that I am still unable to get resistance in pedal and cannot get clutch to engage, if depress pedal with pressure bleeder at 20lbs I get pedal resistance but at 0 I get none, clutch won’t disengage in either scenario
I am at a loss, anyone have any suggestions

[GuidoK]

Your post is not clear to me.
Have you bled the slave cylinder on the clutch?
When you open the bleeder on the clutch slave cylinder, and then depress the clutch pedal, do you get any fluid out?

Official procedure is to remove the slave cylinder from the clutch, and put a special screw clamp on it and you completely screw in the rod from the slave cylinder. Then bleed with pressure bleeder, and then screw the clamp back a bit and in again, bleed again and repeat this a few times. To get the residual air out of the slave cylinder.

My guess is that your slave cylinder is full of air (so no fluid in there at all). The bleeder sits in front of the cylinder, so it's diffucult to get that air out if you can't move the slave cylinder rod.

Maybe, if you don't have that clamp (and can't rig up one) you might manually fill the slave cylinder by removing it, and dripping in fluid (in the bleeder hole or hose hole) while moving the rod by hand a bit, and then fit the cylinder in extended form, and then further bleed the system.

[Westersund]

I've never remove a clutch slave to bleed if and it's worked fine but it takes some time and fluid to bleed the clutch slave, I've say around 1L if you use vacuum.

[GuidoK]

Originally Posted by Westersund

I've never remove a clutch slave to bleed

Neither have I, but I've also never had a completely empty one.
Normally to bleed and refresh the fluid, the clutch spring presses in the clutch cylinder (when clutch is depressed and then the bleeder is set open), but maybe it doesn't press it in 100% all the way, so if that's the case and it's completely empty, there's still air in there.

[3002 tii]

Definitely sound like you got air, a lot of it, in the line

[Westersund]

Originally Posted by GuidoK

Neither have I, but I've also never had a completely empty one.
Normally to bleed and refresh the fluid, the clutch spring presses in the clutch cylinder (when clutch is depressed and then the bleeder is set open), but maybe it doesn't press it in 100% all the way, so if that's the case and it's completely empty, there's still air in there.

I've bled a completely empty slave cylinder using vacuum and it works fine without a special procedure.

[GuidoK]

Originally Posted by Westersund

using vacuum

That might be an interesting difference. The TS uses a pressure bleeder.
Maybe with pressure he's mainly pushing more air in the cylinder (and compressing the air that is already in there), and when releasing the pressure, the air pushes the fluid that managed to get in there out again.

On the slave cylinder, the bleeder sits a bit on the underside and the cylinder is horizontal. Maybe that's not so suitable for pressure bleeding as a brake cylinder where the bleeder sits on top and the feed is at the bottom (well, more in the middle)

[Westersund]

Originally Posted by GuidoK

That might be an interesting difference. The TS uses a pressure bleeder.
Maybe with pressure he's mainly pushing more air in the cylinder (and compressing the air that is already in there), and when releasing the pressure, the air pushes the fluid that managed to get in there out again.

On the slave cylinder, the bleeder sits a bit on the underside and the cylinder is horizontal. Maybe that's not so suitable for pressure bleeding as a brake cylinder where the bleeder sits on top and the feed is at the bottom (well, more in the middle)

That could be right! It's a bit stubborn to get going with the clutch (notice any difference in the pedal) but when it's starts getting better it's a gradual change and you notice a difference between every pass and when checking the pedal pressure after every pass.

I haven't tested a pressure bleeder yet, but I should get one as BMW uses one when the ABS needs bleeding. I've tried that procedure on my M2 with my vacuum bleeder and that haven't worked out or if I'm not good with ISTA (fails when I get to the front brakes).