Judd

iTrader: (1)

I know this has been discussed before,, I tried reading through about a dozen or so thread during a search. Most of the posts delt with how to fix it {'02 slave and a up graded master}.

I would like to know what exactly causes the petal to stick to the floor. My 2000 Firebird is on the stock clutch, it has abot 42K miles now and a absolute crapload {Webster's Dictionary says that a "crap load' is somewhere between 200-250 launches! }. Anyway, the last trip to the strip resulted in my first experience with pulling the pedal off the floor.

Today, I met up with a SRT10 Dodge and kinda got into a bit of play. Both of us pulled out to pass a car when a passing lane opened up. Started accelerating in 2nd, shifted to 3rd but when I when to shift into 4th,,, the pedal was stuck to the floor. That is the part I don't really understand. I can understand that the clutch would get rather pissed off during a clutch slipping drag style launch,,,, but from a roll???? BTW, I pulled the SRT10 pretty good.

ssjunkie

iTrader: (3)

I dont know what causes it, but mine did it for the first time friday night are the track. Car has like 28K miles on it and approx. 20 track passes. Never any sticky tires either.

2nd run I went to shift to second and the clutch was still on the floor. pumped it a little and it came back enough to shift. Then the next run, after the burnout I went to push the clutch to stop and it was low and soft. Pumped it a couple time and it came back. So I launched real soft and let of for the shifts and it made it down the track. It drives fine on the street, though? Can anyone explain? I have heard something like the fingers on the pressure plate heat up and stick to the slave/throwout combo and dont let it come loose? Not sure i believe that though.

whitecamaross

it is the fact that the line is super thin and doesnt pump enough fluid to bring it back up under heavy load. mine did it 3 times last weekend at the track after i heated up my m/t drag radial tires. dont buy these tires if u have a weak clutch because it is going to bring that clutch to an end. i am going to try to do the drill mod tomorrow morning and see how that goes. i dont know if it is worth the effort though, but ill give it a shot and see if it does help or not.

glennster

iTrader: (1)

clutch disc gets thin and plate over centers

demonspeed

iTrader: (7)

Due to the restriction in the line from the master to the slave, it will cause the fluid to take its time to get back into filling up the line.

Basically, when you are racing and shifting fast, the 1-2 shift goes smooth, but between the time you just hit 2nd and when you're at the top of 2nd, the fluid is having a hard time getting back into the master because of the restriction. When you nail 3rd, the pedal will take even long to come back up because you just pushed the small amount of fluid that went back into the master back into the slave. The restriction is again, not allowing the fluid to come back up in a timely manner, so when you nail 4th, the pedal is stuck to the floor because all the fluid is stuck in the slave and needs time to make it's way back into the master due to that restriction.

This is where the drill mod comes into play. When you drill that restriction out, the fluid is free to travel back and forth quick enough so that it won't cause a hangup between shifts.

This is my take on the situation anyway, so It might not be entirely true. I know the drill mod worked for me though.

ssjunkie

iTrader: (3)

dmnspd, your reasoning sounds logical to me if it did it all the time. How do you account for my 20+ passes up to this point with no trouble at all? If the line was to restrictive, I would think it would have been to restrictive from the start? Also my clutch was on the floor when I went to shift from 1st to 2nd. After I pumped it a little it came back and then the 3-4 shift was fine.

I am inclined to believe it has something to do with excess heat in the pressure plate, somehow causing the fingers not to sping back pushing the throwout/slave back. Which in turn pushes the pedal up. If that makes sense. Its hard to explain in writing.

Judd

iTrader: (1)

I have the same questions as ssjunkie, I had well over 250 launches {way over that if you count AutoX runs} before the problem ever happened to me. It only started once I bumped my power up with a cam and headers. That could have been a coincidence as the motor had around 40K miles when I did the cam and headers.

I also think that it has to do with heat,,,,,, or maybe what glennster said; might have something to do with the clutch getting worn down???????

ssjunkie

iTrader: (3)

I understand thining clutch disk, but what is plate over centering?

demonspeed

iTrader: (7)

Have you looked at your fluid lately? You'll probably notice a bunch of "junk" floating around in the dark fluid (that's supposed to be clear or have a yellowish tint).

I'm mentioning the "junk" because over time, that stuff will build up and clog the lines and the restriction - almost like a clogged artery.

glennster

iTrader: (1)

When the disc gets below a certain point of thickness the PP will "over center" at times and leave the pedal on the floor.We had this problem at 20K,the pedal would at times stick on the floor with no rhyme or reason.Get in the car in the morning,push down and it would stay down,pull it back up and it may be OK for a week.Drive to work,push down for a gear change and down it stays.It had new hydrolics changed by the dealer but the actual fix was a Z06 clutch kit,never has done it since.

BigDaddyZ28

I think that you hit it right there. If a restriction in the line was causing the problem, Then how come it worked fine before?

I think that our clutch pedal return issues may very well be caused by heat...

I was thinking that the heat was causing our clutch fluid to boil. Notice how quite a few of the cars with this problem have headers installed (more heat generated real close to the clutch fluid line) and also consider how old or contaminated clutch fluid boils at a lower temp. than fresh/clean fluid. I think this explains why the problem does not occur right away IMO...

ssjunkie

iTrader: (3)

big daddy, Very true, contamination or just 1000's of heat cycles could degrade the fluids heat tolerance. There isnt very much fluid in the system. Since I dont have headers I would think excess heat in the pressure plate might be absorbed by the fluid in the slave?

Another thing to think about was that the car was moving/accelerating while the pedal was on the floor. Which means to me that the clutch had in fact engaged(grabbed) or that the pressure plate fingers had returned to the normal position(out). So the slave cylinder had to of been pushed back in. Which should have pushed the fluid back in the MC. Finally pushing the pedal back up. Since the pedal didnt come back. Boiling/compressable gas might have been in the line preventing enough back pressure to push the pedal. If that makes any since in writing?

I think this is one of the most plausable explenations yet? any other opinions?

I still am not understanding the overcentering thing? Sorry?

Ryan02SS

iTrader: (3)

I have an 02 car with the Z06 clutch, 01+ slave etc... I performed the drill mod and still had the clutch stick to the floor on the 3-4 shift and you could feel the clutch pedal getting mushy on the 2-3rd shift. I read so many different ways to fix the problem but none worked except for Nine Ball's idea. The braided SS line from the master cylinder to the slave is located very close 1 1/2" to my headers allowing ungodly amounts of heat to hit that line making it extremely hot under WOT. I sliced open a length of 3/8ths fuel line and wrapped it around the braided hose. It seemed to help but the problem was still there. Then I double wrapped the fuel hose over the braided line with 2" wide aluminum tap. Then I fashioned a heat shield out of metal flashing 10" long and used nylon tie wraps to wrap it around the hose where it is close to the header but still allowing enough room for an air space to cool between the line and the header.
I was still skeptical as to if it would help but now after months, I have never had my pedal stick to the floor or had a mushy feeling pedal since I wrapped the line. A huge thanks to Nine Ball!!!!!!! You might also want to try Valvoline Synthetic DOT V fluid also as it has a 500 degree boiling point which is much higher than standard DOT 3. HTH

Judd

iTrader: (1)

Now that is pretty odd that high ambient temps could cause the problem. Don't get me wrong, I know that high temps WILL boil the fluid and the problem did occure after I installed headers but,,,,, on the very first pass with of the day,,,, after the car was cooled down,,,, my clutch stuck to the floor. I just do not believe that boiling the fluid from high temps in the surrounding area of the lines is the case with my car.

On my car,,, I never once had this problem. It should have popped up before. I have somewhere abouts 200-250 1/4 mile runs and dern near that many autoX runs. Many of those runs were several passes in row. Heck I know I did near 15 autoX passes in a row at Bristol. Those runs were dern near hot laps as there wasn't anyone in line. Me and about five to ten other guys were the only ones runing at the time. If high ambient temps caused the problem,,,, it would have happened then.

Don't get me wrong,, the clutch would get irritated with hot lapping. With ET Streets and my style of launching {slipping the clutch out rather than just dumping},,,, I could only get a two to three runs at most before I would have to let it cool for at least a hour or so. The clutch would get hot and start slipping. But not once did the clutch stick to the floor like now.

What changed?????

1. A few more miles accrued but heck,,,, only about a 1000 or two from my last event.

2. I added more power, lots more power,,,, from my last event. I installed a set of headers and a good size cam. My traps went from a best of around 109-110 to around 114-116mph. Maybe the extra power is making the clutch slip as it's going down the strip. As the clutch slips,,, it's building up some heat. Maybe the heat from the slipping clutch is boiling the fluid???

I will say that as of right now,,, I don't really know what is causing it. It may well be a combination of stuff,,,, high milage, worn clutch,,,, old contaminated fluid,,, heat from the headers. I don't know but I'm not going to close my eyes or ears to any ideas. I'm going to try to shield the line from heat {since that is pretty much free}. Maybe I'll try to bleed the clutch also since I always have some Motul 600 laying around. How hard is bleeding the clutch on these cars?

Thanks for everyones ideas on this,,, like I said,,, I've heard of the problem,,, read a few fixes {mostly getting rid of the pre '01 hyd. system} but I really don't think that anyone has just come out and said "The pedal sticks to the floor because ----. Things that I don't understand bug me.

Hugger Z

iTrader: (4)

I too agree with the heat theory. A clutch is friction material. Friction creates heat. Heat cycles will degrade the fluid over time. I think a combination of factors leads to the pedal staying on the floor. DOT 3 fluid boils around 250-275 degrees F. So if you are running lots of power and your clutch is struggling to grab, plenty of heat could be generated and transferred to the fluid in the system. If the fluid boils you get air bubbles, which compress more than the fluid, so you get a soft pedal when trying to shift. If it gets soft enough, there won't be enough fluid pressure to return the pedal. Just my 2 cents.

Oscar Will

Hold on a second guys, heat is always a factor in clutches, but when you are dealing with a diaphram type pressure plate, centifugal force at high RPM can cause a diaphram plate to "stick" like that. That problem has been around for years.....even before we started getting hydraulics involved. Centerforce has made a ton of money with their "weighted" diaphram clutches which apply higher pressures at higher RPMs. Explore this a little bit before you spend any money. The old "Borg & Beck" three finger plates NEVER did this.

WhynotSS

I don't think it's the restriction in the line because mine got stuck yesterday on a freeway roll when shifting from third to fourth. I never rowed through first and second and third. I just started in third, sifhted to fourth, and the pedal didnt come back up.

lemansz

the same thing is happenign to me.. on my ... 02 z06...


10k mile old stock clutch 30k mile old car

Oscar Will

......like I said, it's inherent in the design.

Judd

iTrader: (1)

Well,,, if it's inherent in the design,,,,,,, why did I not have it happen once in the previous 250 or so 1/4 mile passes? I'm not saying that it isn't a characteristic due to the design,,, but I didn't have a single problem with it,,,, then bam,,,, all sorts of problems after adding a bunch of power.