Clutch Hydraulic Issues?

So this is one of my first posts... I am completely stumped and maybe I'm just dumb but here it goes.

I drive a 2007 Chevrolet Aveo LS 4 Door Sedan Manual Trans which I have had since brand new.

At about 52,000 miles the clutch blew up into all 8 pucks and destroyed the transmission and starter and I had it all replaced at the dealer partially under warranty after a month long battle (And many calls to Pakistan, India, etc.).

About 2-3 years ago I replaced the slave cylinder (the head of the piston that presses the clutch fork somehow sheared off).

I am currently at about 125,000 miles.

A few days ago I was driving home from work when the clutch started losing pressure.

The pedal became squishy and I couldn't get into gear anymore.

It was weird because the slave cylinder still pressed out the clutch fork but not enough for it to release.

I had it towed home and ordered a clutch master cylinder (Dorman Part# CM640078) after talking to several friends/coworkers/techs who said it could be an internal seal.

I should mention at this point that there is no visible leak anywhere in any hydraulic line at all. Also the slave still reacts when the clutch pedal is depressed.

When the clutch master cylinder arrived today I (following Mitchell Data Labor) replaced the master cylinder and bled the clutch system through the slave (gravity at first then manually).

Once the system was bled it was still reacting the same way as previously.

I then figured maybe it was an internal slave cylinder issue, or at least figured I could eliminate that as a possibility.

I swapped the slave cylinder for the old slave (but used the non sheared piston) and there was no improvement.

I have bled the system, checked for leaks, and I am completely stumped. Has anyone dealt with this before? Am I missing something?

Its as if there is an air leak somewhere that is not allowing the cylinders to build enough pressure, but I cant seem to find where the leak is coming from. Are there typical spots that leak?

The other possibility is that rockauto.com sent me a defective master cylinder....which is unlikely but not unheard of (I love rockauto.com , but sometimes they send parts out that have been returned and not checked).

Please help?

Did you bench bleed the master cylinder prior to installation?

Nope, how would I do that? I mean with a separate reservoir and all?

It was relatively easy to replace the master cylinder, but I'm thinking there may be another issue.

Also, my friend sent me a post from another forum saying that bleeding the clutch is a bit different than brakes, where you may have to pump the clutch pedal fast with your hand and have someone crack the bleeder while still quickly pulsing the pedal and only seal the bleeder once you push the pedal to the floor. Supposedly this is to get any air trapped in the clutch master out, thoughts?

So, to update:

I bled and bled and bled some more multiple ways, to no avail.

I then moved the car slightly and pumped the pedal to realize the fork went out slightly and froze in place, it won't go back into resting position and it won't disengage the clutch... so is that the pressure plate? Should I do a full clutch replacement?

Should I expect to replace other parts?

Let me make sure I understand accurately, you replaced the master (by the pedal) and then the slave as a test?

So both are new, and appear to be functioning? If you are bleeding them properly, there is a possibility the fork is bent. It sounds like you are hard on clutches. I don't believe the earlier (non ecotec) has an inspection plate either, so if you suspect internal (clutch) damage your tearing it apart anyhow. Might as well replace it all.


I would verify the bleed job is correct. If you did not bench bleed the master, i would disconnect the slave, and then gravity bleed it again. Once you know it is good, then attach a bench bled slave and bleed it again. I only use a power bleed on the clutch. I know a few different methods the different mechanics say works, but If i do any manual bleeding, it is only opening the bleeder with the pedal pushed.

Quote:

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Originally Posted by petrified.rabbit

Let me make sure I understand accurately, you replaced the master (by the pedal) and then the slave as a test?

So both are new, and appear to be functioning? If you are bleeding them properly, there is a possibility the fork is bent. It sounds like you are hard on clutches. I don't believe the earlier (non ecotec) has an inspection plate either, so if you suspect internal (clutch) damage your tearing it apart anyhow. Might as well replace it all.


I would verify the bleed job is correct. If you did not bench bleed the master, i would disconnect the slave, and then gravity bleed it again. Once you know it is good, then attach a bench bled slave and bleed it again. I only use a power bleed on the clutch. I know a few different methods the different mechanics say works, but If i do any manual bleeding, it is only opening the bleeder with the pedal pushed.

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After all the bleeding, bench, gravity, etc. and reading what you and others have written, it seems as though my clutch forks are bent. I plan on taking it to a shop (with the necessary parts fdine repair) and having them do the job, as I'm not sure I have the patience for doing the job on jacks in the driveway.

I have come to the realization that I am not gentle on clutches (though I will say that the first one was when I was learning stick and I was not nice to it) and I have no idea what the dealer put in the car as a replacement and if the trans was new or used. I don't really have great feelings toward the dealer who did the work but they were closest.

Where do I get the replacement forks and what clutch would be the best replacement?

Since you are not 100% where the damage is, I wouldn't buy anything. These are pretty specialized parts, I imagine some are dealer only.

If they are opening it up, depending on the amount of time you have to wait around, I would get a stage clutch (sprung) off eBay. 2-3-4 whichever sounds like how you drive..

SO just an update...It was a bad throwout bearing that was seized causing the for to be misaligned and everything to cease functioning. Not sure how me being hard on it caused that but I suppose its possible. Either way the replacement wasn't terrible, but I don't believe the people who say they can do it quickly because even with a lift, engine support, and trans jack it was a pain in the butt and took a while- I suppose if you've done it a dozen times and know the perfect intricacies of how to properly angle everything etc. you could do it "quickly" but it wasn't fun especially solo-ing a lot of it.