Help me diagnose my funky clutch issue

[Antilles]

The problem is either in the hydrolic system or pedal assembly.

I have an ACT 2600, SS clutch line, new master cylinder, and the slave looks alright. New slave cyl. rod, new clutch fork, and new pivot ball.


This problem occured while driving normally. I shifted from 2 to 3 just fine, but the next time i went for the clutch, it was rock solid (About double what i would consider normal for a 2600). It returned to the normal height. The next time i pushed the clutch in, it came only halfway up. The clutch remained rock hard. I can pull back up to the stock height, but the first half of the travel is just mush. It may be worth noting that it is very hard to pull it back to the stock height.
Also, with the clutch so close to the floor, it doesnt completely disengage anymore.


I have a few theories, but im looking for experience with this sort of problem or any suggestions.

I thought the slave rod might have bent slightly, but I check that and it seemed fine.
There was a small amount of fluid in the slave cyl. boot, but im not low on clutch fluid, and the tranny was covered with snow, so its probably water. Besides that, this doesnt seem like the normal way for a slave cyl. to fail.
The lower hard metal line to the slave is kinked. It has been this way for a long time and driven just fine, but who knows. I am trying to reason out how a kinked line would cause my symptoms, and it seems the best bet right now. unfortunately the only way to test that is to replace it, and i'd like some suggestions first.
Pedal assembly - i must admit that i know nothing about how or why these fail, but i hear that it happens once in a while on 2600 equiped cars. Just throwing that out there for input.

This is already long enough to put most people to sleep, so i'll quit for now and see if anyone comes up with something.

Thanks,

Chris

 

[Defiant]

My guess is that you've adjusted your master cylinder pushrod to a point that blocks the return port. When you press the clutch in, it pumps up the system, then locks up.

Next suspicion would be a failing throwout lever.

 

[Antilles]

I *think* i've got it.

It is possible for the kinked line to have become "more kinked." If that were the case, I think that my symptoms are spot on:

Line gets kinked, so the clutch gets rock hard. The additional restriction makes it very hard to push the clutch in.
Once all the fluid gets past the kink, it has a very hard time coming back (clutch doesnt come back to the top). It only comes far enough up to JUST get the clutch off the flywheel.

Good news is that hard line is only $6. It gets here tomorrow, and I will update with how it went for me.

Thank you for your suggestion Defiant. If this leads to a dead end I will check out the master cylinder adjustment.

Thanks,

Chris

 

[Morphius]

Too start with, with your ACT 2600 is seriously overworking the clutch pedal assembly. The variance in the pedal location, on clutch actuation, is due to the slop in the assembly due to years of use and now it VERY overloaded by the ACT clutch. Get it welded ASAP. See this thread for pics I posted:

http://www.dsmtuners.com/forums/showthread.php?s=&threadid=3266

The kink in your line doesn't help, but given it worked OK before, it should work the same with the new clutch.



-DaimlerChrysler Engineer

 

[Morphius]

Originally posted by Defiant
My guess is that you've adjusted your master cylinder pushrod to a point that blocks the return port. When you press the clutch in, it pumps up the system, then locks up.

Although a good guess, this is not the problem. This is where my industry expertise kicks in!! I'm the corporate release engineer for hydraulic clutch systems for all of DaimlerChrylser Trucks. If an issues arrises at a plant, dealer, etc. I'm the engineer they call first. So, needless to say I know a thing or two about hydraulic clutch systems. I'll admit I'm learning new things everyday, and don't know everything, but I do know more than most.

To what you refer to as "pump up" is actually an over effeciency error of the system. Think of the system from the reservior to the slave cylinder as a continuous line with a "T" at the master. With no load on the pedal, the fluid is allowed to "flow" to and from the reservoir to the slave. Upon the first 1/2 inch of pedal actuation, the master cylinder compensation valve (a small valve on the end of the master cylinder piston blocks a "leg" of the "T" so that no more fluid can flow to the reservior but still travels to the slave cylinder. In a case, where the pedal has "preload" or has been adjusted so the the slave is partially acutating the release lever before the clutch pedal is pressed, the compensation port is closed off. This means that you get that added 1/2" (or so) of piston travel (which equates to an added volume of fluid you are pushing) In the end, this means you put the same amount of pedal travel in, but get added travel out at the slave cylinder.

When this happens, the system has created a vacuum on itself. As your clutch disc wears, the hydraulic clutch system needs to compensate and adjust itself. (ie. my referance above regarding the fluid flowing from the reservoir the slave with no pedal input) If your pedal has been adjusted with this condition, the hydraulic system will not adjust. (over the life of your clutch disc, the slave cylinder rod will move into the slave body.... getting shorter) In the end, because the column of fluid you are pushing with the hydraulics is the same (no change in pushrod length), you are actuating the clutch diaphram less and less. Over time you will be releasing the disc, less and less. Walla, a burnt up clutch disk.

That above applies to a conventional clutch. A self-adjusting clutch (SAC) is another story. SRT-4's and Trubo PT's have SAC. But I won't dig into that.

Anyhow, hopefully someone found that bit of information interesting.

-DaimlerChrysler Engineer