More clutch actuator trouble! plz help!

[kevin-design]

Ok, so I posted recently on the troubles I've been having with my clutch- where you can pump it a few times and then it eventually sticks and won't go to the floor. Well, first I replaced the clutch master cylinder, just 'cause it was available in town. Nothing much changed. Then on observing that I could get full travel and observe the moving fluid when I disconnected the clutch slave, I decided that was bad and replaced that too.
Now- after like 2 weeks, and two new components, I'm back to square one. That in itself sucks, but what sucks worse is the implications in my head. To me what this indicates is that the slave is hyperextending and reaching a limit. The only way that could happen is if there is some deformation/damage/dislocation of the clutch fork..? Maybe the ball stud?
Prior to all this happening, everything was fine. Quite suddenly, I was able to depress the pedal to the floor, and not able to actuate the disc. However there was never any noises, no 'pop', no grinding- nothing abnormal except my lack of clutching ability. When I got it home, I discovered the reservoir was out of fluid.
That about sums it up. I'm bracing for bad news, but was also someone has had a similar experience and could shed some light on the possibilities.
Tonight, I'm going to try and wrestle the transmission cover off so I can get a firsthand look of the mechanical situation. Thanks for any help!
-kevin

 

[-=Jeff=-]

Ok, so I posted recently on the troubles I've been having with my clutch- where you can pump it a few times and then it eventually sticks and won't go to the floor. Well, first I replaced the clutch master cylinder, just 'cause it was available in town. Nothing much changed. Then on observing that I could get full travel and observe the moving fluid when I disconnected the clutch slave, I decided that was bad and replaced that too.
Now- after like 2 weeks, and two new components, I'm back to square one. That in itself sucks, but what sucks worse is the implications in my head. To me what this indicates is that the slave is hyperextending and reaching a limit. The only way that could happen is if there is some deformation/damage/dislocation of the clutch fork..? Maybe the ball stud?
Prior to all this happening, everything was fine. Quite suddenly, I was able to depress the pedal to the floor, and not able to actuate the disc. However there was never any noises, no 'pop', no grinding- nothing abnormal except my lack of clutching ability. When I got it home, I discovered the reservoir was out of fluid.
That about sums it up. I'm bracing for bad news, but was also someone has had a similar experience and could shed some light on the possibilities.
Tonight, I'm going to try and wrestle the transmission cover off so I can get a firsthand look of the mechanical situation. Thanks for any help!
-kevin

Welcome to the world of Bad Master and Slave Cylinders.. I got my vette back together and I am nto fighting a similar problme with my 89, but mine clutch is grabbing way too low, with me it is a bleeding issue, bnot all the air is out yet.

For you it sounds like on of the new pieces is bad, did you change the hose when you changed the cylinders? You also must be 100% sure that the system is bled and working at 100%. I have tried a bunch of different ways to bleed mine. within the last 2 weeks I have swapped the Master twice (third one is going in tomorrow) first 2 were bad. I bought a new slave and was bad before I installed it. I have a new slave coming tomorrow as well. I will install the slave and master and try yet another form of bleeding them in hopes it fixes my issue.

A good place to check for proper bleeding (other then the GM manual, is www.zfdoc.com you can also email bill B. Great person to talk to and will help you out.

 

[kevin-design]

thanks!

Hi- thanks for posting! I would LOVE for it to be a bad master or slave cylinder, I mean since those are warranteed parts and all, that's a zero part cost (at this point) - and despite the nastyness of the actual job, relatively little labor when compared to yanking the trans out again. Anyway- to your questions, no, I didn't replace the tubing- didn't really see the point as it was apparent that fluid was freely flowing through it. Pressing the pedal with no slave cylinder and just a clear tube produced a smooth flow of hydraulic fluid all the way to the floor, then retraction with the pedal.
What I'm really most interested in learning is what causes these symptoms- where the system is failing- its as much curiousity as a desire to have 4 wheels again. Going through the possibilities in my head, all I'm coming up with is a possibly hyperextended slave cylinder, and that only makes sense if the fork is somehow out of place. I'm eager to hear other ideas. I had to work late tonight and so couldn't crawl back under there to investigate further tonight- hopefully will be better informed with some forum help when I do get to it (tomorrow?).
Following a trans swap previously, I was able to bleed the system very simply (thanks to forum advice) by simply pressing and releasing the pedal (300x or so). What's happening now just doesn't feel right, but originally, it was pressing with little or no resistance. :confused

Welcome to the world of Bad Master and Slave Cylinders.. I got my vette back together and I am nto fighting a similar problme with my 89, but mine clutch is grabbing way too low, with me it is a bleeding issue, bnot all the air is out yet.

For you it sounds like on of the new pieces is bad, did you change the hose when you changed the cylinders? You also must be 100% sure that the system is bled and working at 100%. I have tried a bunch of different ways to bleed mine. within the last 2 weeks I have swapped the Master twice (third one is going in tomorrow) first 2 were bad. I bought a new slave and was bad before I installed it. I have a new slave coming tomorrow as well. I will install the slave and master and try yet another form of bleeding them in hopes it fixes my issue.

A good place to check for proper bleeding (other then the GM manual, is www.zfdoc.com you can also email bill B. Great person to talk to and will help you out.

 

[muddywaters]

Clutch

Hi, There are power bleeders for clutches available. Muddywaters

 

[-=Jeff=-]

How does the pedal feel now? where is it grabbing at (when releasing from the floor)??

My guess is that there is an issue with the hydraulics, if I recall you installed a clutch last year then drove the car a good distance, with no troubles with the clutch right? If so, I am guessing that it is still in the Hydraulics. What makes you think it is hyper-extending?? When you installed the new slave, did you need some pressure on it to get the bolts on? you should also have some resistance when you depress the clutch, it should disengage towards the top, if not it is more then likely the Hydraulics (master or slave or Both)

Like I said, I am installing #3 master and #2 slave this weekend in hopes to have a good clutch system.

 

[kevin-design]

Hello,
Currently, I can't get it to the floor! It stops about halfway down, and possibly if I wanted to I could use my superhuman strength to push it to the floor but something else would probably break.
Yes, though its true that I drove it to chicago and back (trouble free- knock on wood) just after a clutch swap. The only thing that makes me think it's hyper extending is that I've crossed off all the other logical options in my head. No, I didn't need any pressure to get the bolts on- further suggesting maybe a recessed fork? I did write your suggested contact, and read his instructional page in detail, but still am mystified.
I'd like to get to it tonight, but its A)Friday and B)Cinco de Mayo.... though there's been talk of a boycott....
Thanks for the help!
-k

 

[-=Jeff=-]

Sounds like a slave problem. When I bought a new slave last friday, I compared it to the old one. the old one's push rod was about 1" further out then the new one. Both side by side on the bench. it looked as if the piston was set to far back int he bore and not allowing the full motion like you are experiencing. Assuming you still have the old slave compare them side by side.

if the push rods are extended the same, then it may be a bad Master

 

[kevin-design]

ok, so I crawled back under and took off my starter, the cover plate, and the slave cylinder. I also took apart my old slave to look for signs of damage-a little corrosion and rust but nothing glaring... I couldn't see as much as I'd hoped mechanically- just the engine side of the flywheel really. When I removed the (new) slave cylinder, the lock ring (the star shaped one) had come loose, and the cylinder did appear to be bottomed out. The rubber cover, washer, and pushrod were just sitting there. There was no pressure on the bolts when removing the cylinder.
I put my finger into the hole of the slave cylinder mount and felt the fork. It felt secure in its postion, but I would like to know where it should be resting relative to the mounting flange. It's hard to access, but I can take a measurement to confirm that the socket that the pushrod fits into is not where it should be (or it is).
thanks for any further help!
-kevin

 

[-=Jeff=-]

PLease measure it, I will measure mine tomorrow and we can compare notes..

I did have a bent clutch pedal so I am behind on trying out my parts

 

[kevin-design]

I measured about 2.9" from flange to the bottom of the cup within the fork, not including the metal spacer piece. Now, I'm off to try out my home made actuator (3 holes in a .25" steel strip, the center one threaded with a 5/16" x5" carriage bolt)

 

[-=Jeff=-]

I knew I forgot something.. but that sounds about right from when i looked at it the other night..

 

[Hib Halverson]

After reading all this, I think you should know that there is an inordinately high rate of DOA clutch slaves for late C4s. That new one you put in may have been bad, too.

But, if that's not the case, I would not rule out a mechanical problem inside the clutch housing.

You might try one more slave but if that doesn't solve the problem, I'd pull the transmission, get the clutch housing off and inspect your clutch.

 

[kevin-design]

Man I would so love for you guys to be right and for myself to be completely wrong on this one- however, I tried out my home made actuator last night, put the car in gear and attempted to rotate the back tire (its off the ground)- no deal. However, when I put the car in neutral, I can rotate it. This further supports my theory that one of the following is true: A) The fork is bent/broken B) The Ball stud is broken/unscrewed C)The fork has somehow disengaged from the throwout bearing or throwout bearing has been somehow liberated from the pressure plate.

As for the slave's reputation, I would be interested to know how its failing or failure-prone (as an engineer). Seems to me a fairly simple device- pressure builds behind the sliding cylinder and actuates the pushrod. So, when failing, does the cylinder bind? the seal leaks? something bends/cracks? Visual inspection of the parts doesn't seem to indicate anything suspicious.
I'm ****ed that I'm going to have to take out the transmission (again), but it sure looks to me that that's the case. oh well.

 

[-=Jeff=-]

As for the slave's reputation, I would be interested to know how its failing or failure-prone (as an engineer). Seems to me a fairly simple device- pressure builds behind the sliding cylinder and actuates the pushrod. So, when failing, does the cylinder bind? the seal leaks?

Yes to all but the bends and cracks..

Same with the Master.. I am getting #4 this week.. first 3 had different problems.. My clutch will work when it is bled right, in fact it did with the current master for about a 1/2 hour, but the Master is leaking where the Tank meets the metal body. I will have a new one on Friday.

GM just makes/designed a crappy pair of parts for the clutch for the ZF..

 

[-=Jeff=-]

Kevin what is your latest status?

My Master I got friday did not work, I ordered another Master and slave today.. will have them Wednesday

 

[kevin-design]

I still have to get the transmission off. I've been out of town and then came down with the flu or I would have got it this weekend. I would bet money that your problem isn't with your cylinders, but really its just my speculation. One thing I did realize is that there is what appears to be a view hole in the side of the bellhousing right beside the fork, so I want to try and get a camera or mirror in there somehow. I haven't confirmed that this hole actually exists in mine, but it exists in one that I replaced that I think was a year or two newer.

 

[-=Jeff=-]

I still have to get the transmission off. I've been out of town and then came down with the flu or I would have got it this weekend. I would bet money that your problem isn't with your cylinders, but really its just my speculation. One thing I did realize is that there is what appears to be a view hole in the side of the bellhousing right beside the fork, so I want to try and get a camera or mirror in there somehow. I haven't confirmed that this hole actually exists in mine, but it exists in one that I replaced that I think was a year or two newer.

Why would you say that? the Master I replaced on Sat was visibly leaking. Knowing that the system worked with it tells me the mechanicals are fine.

I have been emailing with ZFDOC, he sent me an email last night that the Slave cylinders have the seal in backwards, which will cause problems. On anther forum (CF) I have a post as well, many guys had the SAME problem or similar to me, new parts fixed it. The 2 new pieces I am getting are aftermarket CAST piece as opposed to the failure prone GM JUNK Drawn Over Metal Pieces. I will find out this week end if they work.

Like I said the clutch works fine, on my car, it just grabs low. I bled it last week, it worked, sat for a day, did not work, within 15mins it worked again, 2 hours later it did not ( when I say did not work I mean grabbing low) that is when I found the Leak.

The Master I put in Saturday I could never get a pedal, it just did not feel right, like there was little to no resistance, that tells me Hydraulic problems.

With your issues with the slave OUT and disconnected does the pedal travel to the floor?

 

[-=Jeff=-]

Kevin,

check this out:
http://corvetteactioncenter.com/forums/showthread.php?t=84204

 

[kevin-design]

the culprit

Ok, after finally wrestling off the transmission again- I've come to discover it was door #3- the flange on the throwout bearing separated from the rest of the slot that the fork engages. This situation allowed the slave to hyperextend as a symptom and also to leak fluid.
Anyone ever hear of this throwout bearing flange being a weak link in the system? It seems like a very unlikely problem to me, and not something that would be likely to fail. Also, since I have everything off again, I'm noticing that once again the pressure plate and flywheel surface appear to be splotchy burned. They're not exactly warped per se, and you can't feel any surface variations, just visable-but they have the same indication of heat damage that I've observed over serveral installs of different parts. I've come to accept this as typical despite advice to the contrary since this has been observed each time. Is there anything I can do to address this? I figure now would be the time since I have everything off again. thanks!
-k

 

[kevin-design]

hey jeff-
yeah, that seal reversal would definatley explain the problem! glad you figured it out, sounds like we've both solved a mystery this week!
-k