'89 ZF w/original clutch to my knowledge...

Went to drive to work yesterday, no clutch pedal at all. No warning, no noises. Clutch won't disengage, the pedal has no resistance. Pushing the pedal feels the same with the clutch master attached and unattached.

A little background: the slave has been leaking for the past few/three months or so. I just keep the reservoir topped up and haven't had any issues. It did have fluid yesterday.

Thinking it was the clutch slave, I bought a new one - a cast Bendix with the bleeder at 10:00. Took pretty much forever to get the old one out and the new one in. Same result - no pedal at all.

When I removed the old slave fluid came out of the clutch side of the cylinder, so it did have an internal leak. I pushed on the clutch fork and it didn't feel loose. When i reinstalled the slave I felt for the rod to make sure it was engaging the clutch fork and felt resistance when i pushed the slave up into the bell housing.

I pulled the clutch inspection plate but I really don't know what I was looking for or expecting to find. All I saw was flywheel.

After the slave was installed and still didn't work, I pulled the clutch master off. Pushed on the rod while I held my finger over the outlet and felt pressure.

I got fluid out of the slave bleeder so I know fluid was passing through the system.

It's my daily driver for the moment, not my ideal but it is what it is.

Any ideas? I'm pretty much at wits end after thrashing for 9 hours on this thing. Would the master provide enough pressure to feel with the finger test but not provide anywhere near enough pressure to move the fluid/slave/pressure plate?

Kevin (centralcoaster) should chime in on this soon, he knows quite a bit about the zf6. Me, on the other hand, not so much

Matthew

I honestly can't say. My first thought was the throwout bearing but that will eventually build up pressure as you pump the pedal and then turn rock hard as the slave fully extends, and will reveal itself when you check for slop at the fork.

It sounds like the system isn't building any pressure and has air in it, but those usually don't happen suddenly.

I would take the slave and hose off and hook it back up to the master so they are laying in the engine bay. This will allow you to try bleeding and testing the hydraulics right in front of you without crawling back and forth under the car or relying on 2 people.

Actually take another look at the fork. Sometimes the throwout bearing flange can crack and bend back to where the slave can't press on it... yet it will still hold the fork in place.

The slave pushrod should have to be compressed as you install it. If not, the fork is too deep from a damaged throwout bearing.

Try pushing really hard on the fork divot with something and see if it gives way. You might need a dental mirror and small flashlight to really check it though. There's a hole in the drivers side of the bellhousing you can get your eyeball in, if you can find a way to get light in there. Maybe through where the inspection cover was.

The slave might be leaking because it extended past where it normally does (due to the new fork position) and that part of the cylinder wall is pitted/corroded and allowing fluid to leak past. This is common with the steel DOM slaves that have aluminum pistons.

If it is the throwout bearing unfortunately you're going to have to pull the trans.

Quote:

I've seen the ears that hold the bearing break off on a couple of arms, not on a C4 but, can happen. The pedal went to the floor on those too.

Yeah but if that was the case the fork would be loose in there. It's still holding onto something.

jmarty, how much clearance is between the fork and the bellhousing in front of it?

it sure does sound mechanical.

The fork should only be an inch or so in from the outside hole. This means the rod compresses quite a bit inside the slave.

Have you heard any scraping of strange wooshing sounds from the clutch area of late?

An inch sounds about right. And there isn't much room for error in there. Even an extra 1/4" wouldn't be too noticeable by eye but would make the car undriveable.

OK....

The fork is only about an inch inside the bell housing and I could feel the slave compress quite a bit.

I went back and did as suggested in post #3. Since I can't get parts until at least Tuesday, I thought what have I got to loose at this point. Time is about all I have.

Pulled the whole system out, did a bench bleed on the master, hooked the system together and bled. Reinstalled everything.

And, since all I have it time....

...I took that rubber cup out of the master cylinder, filled it all the way up with fluid and walked away.

This evening I could feel a little resistance in the pedal about an inch off the floor. At that point I kept pumping and pumping and pumping the pedal.

D@mn thing works now. There must have been some air in there I just wasn't getting out. I thought it really strange that I didn't get any pedal at all after bleeding. What ever I did bleed wise the first time around seemingly had no effect. That's never happened to me before. Usually I get some sort of pedal, even if it is a little spongy.

Live and learn, I guess. Pretty sure going back to post 3 above got me there.

Thanks!

yea, air will do it...

I used a brake bleeder tool, to draw fluid down when I did mine last. Did the bleed in a matter of 10 minutes!

But, your's sure did sound mechanical. How many miles on the clutch itself?

Not sure how many miles are on the clutch, I suspect the clutch is original, 155k+ on it.

My fear, too, was something mechanical.

I didn't have any sort of bleeder tool to work with. What did you use to draw fluid out? From this experience, I can see how forcing fluid up through the system would work. The easiest position to get the slave into while still attached to the hose on the car was bleeder down. Slave attached to the bell housing, forget it. Bleeder is right up against the tunnel.

It just seemed strange that I didn't get any pedal with the little bleeding on the car I managed to do. Usually I manage to get something.

the hydraulics here are very finicky. They defy logic, really.

I agree, some bleed should result in some sense of accomplishment, but it takes a system working at nearly 80% to get that! The clutch requires a lot of pressure... And the general design is marginal at best.

If you have 155k miles on an OEM clutch, that, my friend, is a record. They are known to only last 125k if driven gently. How long have you owned the car?

There is a tool called a Phoenix Injector. I don't have one, but I do have a vacuum bleeder pump. It's a hand pump that draws fluid down. It worked like a champ when I did mine last summer.

I'll check out the Phoenix injector. I should do the clutch master sooner than later, especially since the price is right compared to a failure.

The car's been in my keep for two years.

Yeah, I'm famously easy on clutches. The '97 LT1 Trans Am is at 160k+ on the original clutch. I was over 200K on my 4-cyl Fox body Mustang!

I can see 200k on a 4-banger...

I am pretty gentle on clutches, too, but not THAT gentle! Impressive.

You are going to run into the nasty reality of the dual mass flywheel, tho... that is what usually dies by 125k miles. I don't have the time to rehash it now, but check the C4 Tech FAQ at the top of the page. It has commentary on the DMFW.