[QUOTE=Ranger;1560286077]^^^ Ken, If the fluid is black and contains particulate matter, it is corrupt. You cannot go from pristine to corrupt fluid in one pass through the gears.

I recently went from pristine to the start of pedal woes in 1200 miles of highway driving with a lot of strong 2-3 and 3-4 shifting but no launches. Six flushes with pedal pumps in between and I made passes at MIR with a normal clutch pedal. LS7 clutch 450 rwhp with 11K street miles and 73 passes at the drag strip, more than half on DRs.

390 rwhp should be fine with Pristine clutch fluid. Pristine means clear and clean after 20 pedal pushes.

Which brand brake fluid are you using in your clutch?

Ranger[/QUOTE

I'll make sure I do 20 pedal pushes when I flush it again this time. I know it was clean though, as I had JUST flushed it to clean. I used Prestone DOT4 synthetic. This time I am going to use some fancy blue stuff thats is suppost to be the "best".

-Ken

 

[QUOTE=Scoundrl;1560286533]If that's ATE SuperBlue Racing, you ought to reconsider. That's because the color is such a dark blue, you can't tell when it changes color. If you want to go to ATE, suggest using their amber colored fluid. I personally ran SuperBlue in my 01Z and changed to another brand for that reason.

Prestone DOT4 is what I am using and as it degrades it turns a dark yellow then amber. It should produce good results if you stay at it until it's pristine after 20 pedal pushes.

Ranger

 

Reminder, if you're putting in a NEW clutch (or slave), install the LAPD (or similar) remote bleeder so you can easily flush your fluid properly. I had CT Corvette install one on mine when he did the Tex and I never regretted spending the extra $.

 

As the Ranger says, heat is the enemy.

The only other time I have seen the black fluid phenomena is on my Pantera. The stainless hydraulic clutch clutch line goes right underneath the headder. The fluid turns black after some cooking .

I have disassembled a Clutch master and the seals are not broken down. So I conclude the black is the fluid a cooking away.

I used to use Castrol GTLMA because it is DOT4 and has a higher temp rating than the stock dot3. However here in NAZ everything including gtlma is hard to find.

I have recently converted everything to the valvoline supersyn Dot4. It is readily available.It has a higher temp rating than gtlma.

It seems to work great in everything, cars, bikes etc.

As soon as it starts to turn color, purge the fluid.

RG
AZ

 

Here is Gm's Tech Bulletin:

Service VME - Hydraulic Clutch Fluid Discoloration #PI00204 - (Jul 11, 2002)
Service VME -- Hydraulic Clutch Fluid Discoloration
.

When servicing the vehicle with the VIN you entered, the following diagnosis might be helpful if the vehicle exhibits the described symptoms.

SERVICE VME
This is a service VME involving 1997 through 2002 Corvettes. Comments have been received about the fluid in the hydraulic clutch system being discolored. This discoloration is the result of carbon black used in the seal manufacturing process leaching out into the hydraulic fluid used in the clutch system. The discoloration may also collect on the inside of the clutch reservoir at the top of the fluid. This discoloration does not affect the operation of the clutch system and should not be considered a reason to flush the clutch hydraulic system.

Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance. This diagnostic approach was developed for the vehicle with the VIN you entered and should not be automatically be used for other vehicles with similar symptoms.

 

Old and still very wrong. Unfortunate to keep posting the that bad info, leading owners astray.

That was five years ago. Since then GM released the C6 with heat wrapped clutch hydraulic lines and DOT4 fluid in the clutch while still using DOT3 in the brakes. So GM certainly has grown to understand that heat is the issue with clutch fluid. Now they need to do the redesign to get the slave (clutch actuator) out of the bell housing oven. Perhaps on the C7. In the meantime, keep changinge that clutch fluid...for a healthy pedal.

To the guys with black clutch fluid and no pedal woes...Better never allow an aggressive driver to run through the gears in your car. Missed shifts and tranny damage will result....

Ranger

 

I still don't buy the fluid as an explanation.

I can drive my car normally forever and never have the pedal stick. But if I run it to redline once or twice, it is almost guaranteed to stick the next time I depress the clucth...even if that doesn't occur until WELL after the last shift.


Example: 2 weeks ago, I took a friend out for a quick spin in the car. Took off from a light, went WOT, shift to 2nd at 6500 fine, shift to 3rd at 6500 fine ....then I basically let the car coast down a good half mile or so until I had to stop....I arrive at the stop sign, push in the clutch at about 1500 rpm, and it that's when it stuck. Any instantly built heat had long been disappated by the time this happened.

I drove the car around town just fine for the next week, not beating it, no problems whatsoever.

Last weekend, took the car out for a group cruise, pounded on it up 3rd gear, stuck again at the 3-4 shift.


The fluid appears clean. If the fluid was so bad to actually cause a sticking situation, it would not be so rpm dependant, it would be a much more more consistent problem. I can purposely slip the **** out of the clutch all day long, and not have this problem, as long as I do it below 5k rpm. Maybe that wouldn't create enough heat compared to a 1/2 second of clutch engagement during a high rpm shift?

Another thing about the fluid...I work quite a bit with hydraulic equipment in my line of work, I know very well what burnt hydraulic oil smells like. If it truly were the fluid being burnt, you'd gag from the stench as soon as you pop the reservoir cap. it is a very strong evil odor. Another reason I do not believe the fluid discoloration is a result of intense heat causing the fluid to boil/burn. If the fluid really were boiling, chances are also good it would more trouble pushing the pressure plate than releasing it, as that is when it's under more pressure.

Besides my personal observations of this issue, I know of at least 5 other people that experienced identical problems immediately following a major power increase. They all tried the repeated fluid changes. Wasn't successful for any of them. They all eventually put new clutches in..and their problems were solved, with no more worrying about daily clutch fluid changes.

One thing no one has ever been able to explain, is why fluid in such poor shape always performs flawlessly under pressure (clutch pressed), the pedal pressure and engagement feel never changes, clutch release point never changes, but the problem only surfaces when the fluid is not under significant pressure (clutch released)....I would really love to hear the technical reasoning of that.

Think of it like this, put some crappy contaminated burnt oil in a floor jack, and go jack up your car. Then release the jack....do you honestly expect the car to stay in up the air? If you do, and you'd blame the fluid, explain why.

In the above question, although the hydraulic principles involved are identical, the only variable between the two scenarios is the source of return pressure. Gravity vs spring.
We can assume gravity will always be there, so of course we expect the car to drop when the jack is released, no matter the condition of the hydraulic fluid....but in a clutch, no one ever seems to blame the source of the return pressure as the cause of this, which is the pressure plate.

 

I have solved sticking clutch pedals for many, many owners at the drag strip by spending 15-20 minutes cleaning up their clutch fluid. Folks I'd never met. Has worked every single time. No exceptions. After the teatment, their pedals remained normal for the remainder of their passes that day.

Ranger

 

Y2Kvert4me, since you work some with hydraulics, how's this scenario sound?

"When the fluid reaches the boiling point (which is lower when contaminants are present) it creates gas bubbles. These bubbles take up space and push fluid back into the master cylinder, which has an open port when the pedal is all the way up. The gas bubbles are compressible, so the next time you try to disengage the clutch, it disengages at a lower pedal position or won't disengage at all.
The clutch pedal relies on the clutch diaphragm to push it back up as the clutch engages, but the diaphragm can't, because it's already engaged and at the end of its travel."

Regarding the smell, not all hydraulic fluid is the same. Some are mineral oil based, brake fluid isn't. ATF could be considered a hydraulic fluid, and it gets that nasty smell you mentioned.

 

Yep....heat + break fluid = problems

 

Ok, so if the fluid is really boiling shouln't I be able to pull the cap and burn my finger in this 300+degree fluid? The boiling point on the DOT4 stuff is very high and I should be able to easily scar myself if this is the issue. I'll try in on a couple passes tonight and see.

-Ken

 

Not bad, and I could almost agree with that..but since you agreed with me that the pedal engagement and feel would certainly change if the fluid became turbid and contaminated with air, why don't I experience any of those symptoms? My pedal feel, engagement and release points don't change for me.
The clutch disengages (releases the disc) just fine when this occurs,
I have no problem shifting when this occurs.
I can resume driving only when I pull the pedal back up, otherwise the car goes nowhere. That is the part that makes your theory non-convincing to me.

So, again, my basic question remains; why can't the spring force of the pressure plate force the supposed burnt contaminated fluid back into the master cyl?
If you say because the pressure plate is actually already in a released state, (which would be clamping the disc to the flywheel), then in my example above (about taking a friend for a ride), why didn't the car stall when I rolled to a stop in gear? How did I get it in 1st gear with no effort, and why couldn't I accelerate from that stop until I physically pulled the pedal back up?

I will explain what happened again in more detail..

Took off from a stop sign, rural road, about a 1/2 mile ahead lies another stop sign. I take off in 1st, go WOT or close to about 6500rpm, shift to 2nd, take it up again pretty high (6k+) rpm, shift to 3rd, kept on it for just a short time till it was time to start coasting down (in 3rd gear) for the upcoming stop sign.
I roll up to the stop with my foot depressing the clutch pedal, put it in 1st gear (with no effort), go to take off, and then, and only then I realize the pedal is stuck. The car didn't stall, it didn't go anywhere. I even pointed it out to my friend, "hey look, the pedal is stuck"...I put it in neutral, pump/kick/jar the pedal until it came back up. Pumped the pedal a few times, it felt fine, pushed pedal down, shifted it back into 1st, took off, and all was normal for the duration of your trip.

If the fluid issue caused the pedal to go down, but not disengage the clutch like you explained, none of that was possible.

I've since had this happen 2-3 more times, and I can easily duplicate the results. The above story was the first time it completely stuck on me.


If my experience is radically different than other's sticking problems, I'm sorry for going off the intended topic.

 

Y2Kvert4me and me are having the same issues. We both did heads and cam over the winter our pedals started sticking to the floor after the heads/cam. Seems like more than coincidence to me. I tried the Turkey baster cleaning and I wrapped the slave cylinder fluid supply line and I tried the clutch stop. I went to Indy last weekend, 250 miles each way. My clutch fluid was crystal clear and I even flushed it twice before leaving. After I get to Indy, my clutch pedal stuck to the floor on an aggressive 2nd-3rd shift. Never did that before. always stuck on 3rd-4th shift before this. Also noticed a different type of pressure on clutch pedal when shifting normally, almost as if additional pressure required to push clutch in. The shop owner who is installing my Tex clutch was a vet tech for a number of years and cannot say conclusively what is happening. He did mention a clutch issue on a built 427 CTS-V. He ended up welding up self adjusting fingers on pressure plate to cure that problem. I hope to have a chance to talk to owner again tomorrow when I pick up car.

FWIW, my old clutch looks great, almost new after 23K miles. I never had a slipping clutch issue with this car. I replaced clutches in 1st gen Camaros both small and big block and never had these types of issues. Makes me think it is in the slave or the adjustable pressure plate. Only seems to be an issue when shifting over 6K. Why is that?

 

High rpms are causing the pressure plate fingers to stay pushed in. It aggravates the problem when you shift 2-3-4 and never go under 5k rpm.
The stock clutch I pulled out a month ago that was sticking looked almost brand new, so did the pressure plate. (Ask AZPowerand Sound) I could rev it to 3k in 5th gear at 20 mph and it would lock up.....no slipping.

But I could rev it to 6K and dump the clutch and the clutch would slip and never hook up or break the tires loose even in first!!! This is because the high rpms and weak fingers (lost temper?) of the pressure plate were staying pushed in due to centrifical force. Now the slave T bearing is not touching the fingers and you lose that much travel, hence the pedal travels to the floor before it touches.

Btw, I did NOT replace the master. The fluid is now already dark after 2k miles and the clutch works like a champ at high rpms all day long (Spec3+) only some chatter.

 

Thanks for sharing your comments.

I'm willing to bet this is exactly what Chalky and I are experiencing too.

 

I never tried dumping clutch @ but could make the make the rear tires just spin on a 1st to 2nd shift. Maybe I can get Y2kVert4me to try the 6k launch and test your idea.

Regardless, i like your theory and idea.

I was surprised to see centrifugal weight added to the fingers of the GM clutch, much like a Centerforce clutch.

Also happen to think that there is more than one type of issue going on here. Some claim teh clutch pedal stop works. Others swear by clutch bleeding.

 

I don't think so. The fluid could easily be 300+ degrees in the slave, and still cool in the master. The line is long enough that exchange between the two isn't good.

If this were the case, you could duplicate the problem in neutral. Our problems may not be the same, but I couldn't get it to happen in neutral by repeatedly cycling the clutch at 62-6300 rpms.

The first gen Camaros didn't have a slave enclosed in the bellhousing where it's subjected to heat.
Over 6K? The higher the shift rpm, the greater the rpm drop the clutch has to overcome, so more slippage. You've also spent more time in the highest part of the torque curve.
I never had a problem before installing the supercharger. Shift rpms haven't changed, only the power.

The aftermarket clutch won't slip like the stocker, so doesn't get the fluid hot enough to cause a problem even if it's contaminated.

 

Damn Dave...I'm trying to limp through this season and not have to replace the clutch till winter.

I may test this theory though.....but I hate to push the issue if it truly is a mechanical issue with the pressure plate....one of them times, it just may stay stuck forever.

 

The zone subject to boiling is at and adjacent to the slave (clutch actuator cylinder) inside the bell housing. So once you measure the temp there please post your results.

Ranger

 

OK, good questions. Different from what I and most others have experienced (my clutch wouldn't disengage) so I can't comment.