ZF6 guys:

I cannot get the clutch master cylinder to work.

I had this problem before. The first time I replaced the clutch master cylinder; I could not get the clutch to actuate. A friend; no longer available even by phone (MIA); was able to bleed the clutch (the first time) and make it work, however, I don't know what he did.

When the clutch petal is pushed in, you can hear the fluid move, but the clutch does not move. I have the service manual (GM) and follow it to the letter. I am still not getting ANY pressure at the petal.

Here is the procudure I am following (generally):
1. make sure that the fluid level is good in resivoir
2. push petal down, and hold
3. crack (open) bleeder valve by bell housing
4. close bleeder valve
5. let up petal.

After that, I try the petal, and there is ZERO pressure. NO leaks on this master cylinder and all fluid lines to and from the resivoir.

Any pointers? What am I missing? I still have not got the trans all of the way in there. This portion is vital in my eyes.

thanks

 

I'm not sure I understand the comment above. Is the transmission in the car or at least bolted to the engine with the clutch, pressure-plate & release fork installed?

Are you positive that the slave cylinder actuating rod is located in the clutch fork release lever properly?

You won't feel any pressure at the pedal until that clutch slave cylinder actuating rod contacts the release fork & tries to overcome the springs in the pressure-plate, and I’ve seen those slave cylinder actuating rods “slip out” of the release fork during their install and you end you with a pedal that has no pressure against it ...

:seeya

 

What was meant by that was that the bell housing is installed to the engine. The mounts are bolted up on the engine side.

The trans, however, is about 1-2 inches from being flush on the bell housing. So, if I can get the clutch to "actuate" then the friction disk align and all will fall into place. But the clutch will not even have any pressure at the petal. :boxing

I will look into the slave cyl installation and the interface with the fork, although I am 99.5% sure that it is AOK!

any other ideas?

 

Ok, I'm tracking now.
Double check that actuating rod install, may not be the problem, but I have had one slip out of that fork during the install, & while the slave Cyl's off I would double check the release fork (push on it with something round) & make sure you can't move it by hand...

Check this site/info out & see if it helps.. http://www.zfdoc.com/clutch_hydraulic.htm

:seeya

 

Could just be a u-joint :steering:

 

Everytime I have changed my clutch I have had this problem. The problem always end up being too much air in the clutch master cylinder. The book does not say it, but you actually need to bleed the master cylinder also. To do this, you need to remove the battery and locate the connection for the line running from the master to the slave. Have someone push the clutch in while you loosen the nut to release the air. The last time I did my clutch I got no movement whatsoever. I bled the master cylinder for at least an hour before pressure came back to the petal. Aor would expel, but then it would stop. So that meant more bleeding was needed. When you open the nut for the master cylinder, fuild should flow continuously. If not, air is still in the system.

Hope this helps.

ZZZASY
'96 LT4

 

:iagree:
But I ended up just pumping the clutch pedal a couple dozen times and that purged all the air out of the master cyl.

 

You don't have the slave installed in the clutch housing do you? It needs to hang verticly and freely, with the bleeder at the highest point. Also try tapping on it to help free up any ait that might be stuck. I've had limited success on my clutch system after fixing a busted clutch hose. I plan to give in yet another shot in the spring. I'ts a bear to get all the air out.

 

You might try jumping the clutch safety switch

Good luck :cheers:

 

:iagree: I pumped the heck out of the pedal as my son watched the bubbles finally subside. Its air.. Either in the slave or master. The slave's bleeding is more of a b#$tch. Try pumping hard and I'll bet your assistant will see air in the master!


[Modified by cgtarga1, 3:31 PM 1/3/2003]

 

how did you spin a main?
was it oil starvation? on a road course? or auto-x?

 

Here's a trick that I learned from GK. Once all your components are hooked up, open the master and pull out the rubber inner liner. Slowly depress the clutch pedal. You WILL see the bubbles rising in the master. If you have the slave off, just press the rod into something solid so that it does the samething. Don't even need the later style slave with the bleed screw.


[Modified by h rocks, 2:22 AM 1/4/2003]

 

I just replaced my 91’s master and slave last week – no problem bleeding at all
#1 – you must remove the slave, as installed the bleeder is the lowest point. With the line off, and the slave out - I filled the master reservoir, and slowly operated the clutch a couple times – watching for a steady stream to flow from the line into a pan – ya gotta hustle – it’s just like gravity bleeding brakes, once full and flowing, your master should be set. Slid under the car and hook up the slave – make sure the flex/hard line is tight in the correct position for final assy. With the slave hanging, hold it with the bleeder at the highest point and open it – gravity will do the work for ya – let the slave fill – watch the master level!! In just a minute the fluid will be flowing steady and bubble free – snug the bleeder. I’ll take a plastic hammer and LIGHTLY tap the master to dislodge and bubbles. With the master still off – force the master piston in, to back flow fluid – careful not to overflow the master. From here I buttoned the system up and I’m back on the track.
Warning!! I’m still back and forth on the phone with Tech’s at TRW on this – I received two New clutch master cylinders from GM – falling apart out of the box! I now believe that the snap ring groove is oversize enough to allow the internal retaining ring - push rod-pushrod retainer and piston to just fall out! I had to modify a larger than intended internal snap ring to hold the components properly.
:steering:


[Modified by Roadrace65, 10:26 AM 1/5/2003]

 

First you should have used an alignment tool to align clutch disc when installing clutch.You have air in system and what I have seen done is take a squirt oil can and fill can with brake fluid.hook hose to end of squirt can tube and the bleeder on slave cylinder.pump the oil can forcing fluid up to master cylinder.keep rags around master so don't get brake fluid over spill on anything.this is how it is done where I work on fords and chevies.
Also they say not to shove the pedal all the way to floor but maybe 1/2 to 3/4 way then open bleeder if you do it by pumping pedal.