97coupechuck

Upgraded my stock 06 LS2 clutch to a RAM Powergrip HD with RAM aluminum flywheel because of sticking pedal to the floor at speed doing my HPDE's. First session and maybe halfway thru, the new clutch starts to stick!!
New slave, Motul, etc. Questioned installer/supplier who contacted RAM, sez RAM said that's because you need an adjustable master cylinder. Then they said nobody makes one for C6 yet and they will have one out in month or two? ????
I'm lost as what to do next, today I'm pressing for upgrading to their multidisk, their next toughest clutch.
Any thoughts/comments? Don't have much time as car is taking up time on somebodies lift with trans replacement and it's all apart right now. chuck

sothpaw2

At a minimum I would have them heat shield the all the hydraulic clutch lines plus I would have them install a remote bleeder. This way you can change more than just the reservoir.

I found using Castrol SRF in there was noticably better than Motul. I wouldn't bother w/another clutch as I think this is a hydraulic issue.

PA Z06

I agree, def a hydro issue. Try a diff fluid and be sure to install a bleeder.

floor it

Call RPM in Daleville Indiana,,,,,,,

MJM Racing LLC

Get a new, stock replacement, master. That must be where the issue is. Now that everything else is new, that's the only thing left. Also get the remote bleeder as mentioned above and keep fresh, clean, fluid in it at all times.

I've been fighting similar issues. I haven't replaced anything yet as I'm still collecting all the parts. I have all the hydraulics ready to go, I just need to pick and purchase the clutch and flywheel. The sticking pedal is a hydraulic issue, but if I have to go into the bellhousing to replace the slave, everything in there will be new. I also have a remote bleed line ready to install.

kmagvette

I ran into this issue two years ago at the track. After 1.5 laps the pedal was on the floor.

The problem was dirty fluid. I did the Turkey baster exchange on the fluid. Suck out, fill, pump the clutch 50 times, repeat. Went back out on the track and things were better, got something like 8 laps. Continues the fluid swap a few more times until the fluid remained absolutely clear.

I Have not had a single problem since. Every time I go to the track, I suck out the fluid and replace with fresh, no need to do the pump thing. I have not had a problem since. Hope your issue is as easy to resolve.

97coupechuck

good advice guys, thanks.
a month ago, on the street, I got the sticking clutch peddle starting on 30 k mi. stock LS2 clutch, thought old got old doing HPDE's. So I was able to sneak on local track and really check it out, kept cool clean fluid and still after 2 laps there it was. Sooooo thought it's time to change out. Installed RAM powergrip HD clutch.
And that what brings me up to this point, still sticking clutch with fresh cool fluid with fresh clutch sys.
I'm installing remote bleeder, and insulate all lines and I'll take that advice of changing master cyl as that's all that could be left.
to be continued! thanks for comments all you speed addicts!

stairman

Why is everyone so convinced that it is a hydraulic issue. It only happens at high RPM correct, so is the fluid ok at low RPM.
What about the laws of physics, that if something was pushing back on the release bearing that the pedal would return. Is the adjustable master just a bandaid, a little more fluid flow to help resolve a mechanical problem. If you pick the pedal back up with your toe then it works fine again, correct? so you just fixed the hydraulics with your toe. This problem really needs to be completely thought out before jumping to conclusions.

MJM Racing LLC

In my case I'm convinced that it's the hydraulics because even though the pedal sticks near the floor, the clutch re-engages. The pedal simply doesn't come back up. Therefore, the mechanical movement at the slave and pressure plate must have happened, or at least most of it. I believe the issue is primarily in the master, allowing fluid past the seal(s) which allows the slave and pressure plate to move without bringing the pedal back up. When raised manually, the piston in the master is returned to normal and it works again.

If your clutch remains dis-engaged while the pedal is stuck down, your issue is different than mine.

The only other thing i can think of that could cause my issue woudl be a buldge in the line, btu if that were the case, it would not function properly again after simply manually raising the pedal.

97coupechuck

clutch is engaged when peddle is stuck on floor.
Funny thing, when it was stuck I could lightly rest/touch foot on clutch peddle and race down the track and feel the clutch slowly coming back up as the rpm"s increased and then it would be good for one more shift, then stick.

stairman

Did the clutch disengage to start with, maybe only a small amount of travel happened when you pushed the clutch pedal, therfore there is no force to push it back. If fluid was getting past the seals in the master wouldn't you be leaking fluid out the push rod end.

97coupechuck

well, the peddle would travel full distance and work fine for shifting but then it would stick engaged and i would have to raise with toe or wait for it to come up, if I hand time/space to do that. In other words, I had full travel and fellt normal when peddle was out. When it was stuck on floor, I stll could shift for a while but quickly it would lose any travel and no shifting could occur then. But the clutch was engaged and I couldn't shift
I looked at master and did not see any leaks.

MJM Racing LLC

Here's my theory to explain that.

I believe the master seal(s) are cup shaped so they act like a check valve. The seal in one direction and then let the fluid pass back over the seal in the other direction. Since the shaft to the pedal has a boot seal at the back of the master, the fluid stays in the master (behind the seal) long enough that when the pedal is raised, it's still there to go back over the main seal.

And yes, on mine the clutch does dis-engage, at least enough to shift, when the pedal is pushed in before it sticks.

I think high RPM shifts require more force to move the pressure plate than low RPM and I think most of us try to actuate the pedal faster at high RPM's than we do at low RPMs. Both of these conditions could add to the fluid bypassing the seal more at high RPM.

stairman

You are correct that there is a boot seal on the master and rod, and that space is full of air. If fluid is going into that space it is staying there until full, and it is not a tight enough seal to keep fluid from leaking out. I understand that in most of these situations the clutch does disengage enough to let you shift. But what if when you depressed the pedal that the stroke was taking up a gap between the release bearing and the pressure plate fingers. What if something at high rpm's were pushing the release bearing backwards. What if I told you that an unchanged hydraulic system will act differently with different pressure plate manufacturers. How much does the release bearing move with a stroke of the pedal. I am not trying to start an agruement, I want people to think about all the variables present. I have studied this a long time with my own clutch issues.

MJM Racing LLC

Obviously different clutch, pressure plate and flywheel combos will put the fingers of the pressure plate in different positions and require varying amounts of movement to dis-engage. But there is a spring behind the thowout bearing that is "supposed" to keep it in contact with the fingers. If your set up allows this to work right, and the hydraulics are tight, there should be no "take up" when you start to push the pedal. If this is not the case, then I would say the slave needs to be shimmed or you require an adjustable master and possibly a master with a larger bore. In my case, and the OP's case this problem arose with all stock hydraulics and clutch. In the OP's case, it remained with an alternate clutch.

You may be right about the fluid not getting into the void between the main seal(s) and the shaft boot. How many seals are on the master cylinder piston? If it's two, then maybe the fluid is only going by the first seal and they passing back when the pedal is raised. It wouldn't take much fluid volume to have the effect we are seeing. I haven't actually disassembled a master do see what's inside. Once I change mine, I'll pull the OE master apart and see what's inside.

stairman

Take a release bearing apart and look at it, the spring is external of the hydraulic cylinder and it only keeps the bearing in contact with the pressure plate, it does not force the hydraulics to extend.

good luck with your fixes, I just wanted everyone to think about all the variables.

97coupechuck

Thanks for the input guys, going to get it done today.
I'm 90% sure it's hyd problem and after all the changes it'll work fine. I'm thinking it's the master. chuck