Ranger

Principles of fluid dynamics. There is a pressure creating device at each end of the connecting line. So sequential bidirectional flow is created by the pressure changes at each end. Turbulence in the actuator helps put particulate into suspension.

If there were no movement from the actuator then the reservoir would remain clean. It doesn't. To witness the flow back into the reservoir, rewatch the post-1 video at 5:44. Also read post-93.

There are plenty of pictures on the web of the actuator with the master cylinder attached.

Ranger

KGjevre

Yeah, I did notice the vigorous flow back into the reservoir when I watched the video earlier, it actually surprised me - very important put the cap back on before stomping on the clutch pedal!

and post 93 has some interesting info that is worth repeating.
Seems like even if you take it in to have the clutch fluid replaced you should do this first to get as much crud out as you can beforehand!

Thanks!

MtnBiker09Z

Hmm, so how do you explain that a brand new ZR1 (or any C6) with less than 10 miles has black fluid? I can't imagine there was much "movement from the actuator".

Ranger

Suggest you
(1) reread post-1
(2) watch the video it contains at 5:44
(3) read GM's description of "How the Clutch Hydraulics Work"

Assuming the C6 clutch hydraulics are working properly (e.g. no seal leaks), then on each pedal stroke, there is substantial flow from the actuator/slave to the reservoir.

When the fluid is agitated, discoloration is generally evenly distributed.

Over time, clutch dust tends to accumulate in the reservoir, as can be seen in the picture below.



The black particulate in the fluid is confirmed to be clutch dust, which enters at the actuator/slave. This fact is verified in the following report: Click here to download a copy of the Unovis lab report

Some initial discoloration of the clutch fluid on cars on dealer lots or recently delivered is said to be caused by production-assembly (of the master and actuator) lubricant leeching. On my three Z06s that phenomenon was finished soon after delivery. That is, whatever was going to leech out, had done so. I proceeded to clean up the fluid by reservoir swaps and thereafter keep the fluid clean.

Now, mtnBiker09Z, if you'd prefer to ignore the accumulated knowledge on this subject, while continuing to perform extended street burnouts you've described elsewhere on the CF, then...good luck with your clutch.

Ranger

Jeffthunbird

Ranger,
We conversed about a month ago. I bought a 2007 z06 from a dealer in Texas in January. Tim414 had looked at the car for another forum member and found that the clutch fluid reservoir was empty. The car was owned since new by an elderly couple and it has 20,500 miles on it. Tim added some DOT 3 and everything seemed to work fine. I have driven the car 6 miles as I just brought it from my storage to my house. I thought the clutch engaged near the end of the pedal stroke but now it is about half way.
I just used your procedure to change the fluid. It was amber colored with no floaties. The cap and the inside of the reservoir was clean. I used Prestone DOT 4. I removed the fluid and replaced it 4 times. I pumped the clutch 30 - 50 times with each new fluid change. The last time I removed the fluid, it looks as clear as new.
I was prepared to change the fluid 20 times. I assume that the elderly couple never used your procedure. Am I missing something?
I think I'm good to go. I just wanted to thank you for maintaining the post on what looks like a daily basis.

AreOhBeeC6Z

Thank you for your info Ranger, I've followed your procedure as you've shown and it works great!

tim414

Before I added the GM DOT 3 I cleaned the reservoir and cap vent. It "had" solid particles (black) when I cleaned it and the cap had crud covering it. I could tell the previous owner knew nothing about keeping it swapped and in this Texas heat I'm sure it evaporated .

Glad turned out o.k. I remember the clutch engaging toward the 'top' third of travel. I thought those swaps would cure that. That's what I told the sales manager as well.

Glad the boys liked it...

Thanks for being here Ranger!!

ssspconcepts

Ranger, thanks for the video on this procedure and for sharing your knowledge. I have a 2009 Z06 that I bought new in Oct 2010. It had 58 miles on it when I took custody and now it has 1700 miles. I do not race or drive the car hard at all...and most would say that I nurse the clutch when I drive. At any rate as a new Corvette owner I read all the posts here and other threads and figured I better check my fluid. Sure enough it was black...no floaties but the rubber boot in the cap had gunk around it. I used your procedure and the car drives better than it did new. Thank you.

My question is this: why is all this necessary? And why hasn't GM done something to mitigate the need to do this? It just doesn't seem reasonable that this should be required...especially under the conditions I operate my car. Thanks again.

Ranger

If you never launch the car nor executed high-rpm up-shifts or down-shifts, then the fluid won't see much clutch dust. It's the dust that destroys seal integrity in the hydraulics. So, gentle drivers need just a relaxed changing regimen to keep the fluid dry (avoid water accumulation from heat/cool cycles). Getting the fluid clean/dry the first time is the hardest part. Ongoing maintenance is paced to driving habits.

Ranger

ggins

So how do you explain my 2011 z with 3 miles on it with dirty fluid?

ssspconcepts

Ranger indicates below that:

Some initial discoloration of the clutch fluid on cars on dealer lots or recently delivered is said to be caused by production-assembly (of the master and actuator) lubricant leeching. On my three Z06s that phenomenon was finished soon after delivery. That is, whatever was going to leech out, had done so. I proceeded to clean up the fluid by reservoir swaps and thereafter keep the fluid clean.

MtnBiker09Z

That's BS. The color is from the o rings leaching. Go read about this on the Z06vette forum and quit wasting your time and contaminating the fluid with the stupid changes!

Ranger

Back to that other forum for you.

The black bits that contaminate the clutch fluid are shards of elemental iron and copper sourced to the clutch disc, PP, and flywheel. That is confirmed by study of the dark fluid under electron microscope.

The blown clutch dust sticks to the main shaft of the actuator, which is coated by a sheen of clutch fluid. That dust is squeegeed into the actuator by the O-ring seal on the next stroke of the clutch pedal.

The notion that the clutch fluid is contaminated by frequent changes with fresh fluid is laughable. Fresh fluid is clean and dry. And each swap displaces about 1/3 of the total volume of in the hydraulics.

Dirty fluid kills the master cylinder by abrading its internal seals.

Clean fluid prevents that.

Two things that clean clutch fluid won't fix are
(1) ill-effects of a clutch slipping due to wear or improper capacity for the engine's torque
(2) a master cylinder that's failed due to the (a) dirty fluid or (2) a production defect in the seals.

Literally thousands of Corvette owners have cured or prevented clutch pedal issues at near stock power by performing this simple maintenance task on an ongoing basis. I, for example, have made 275 burnouts and drag launches and 1000+ 7K shifts on my C6Z without pedal issues. Likewise in my C5Zs made 450+ passes without pedal issues. Many other CF members have similar experiences.

Ranger

KGjevre

Well, you can do this procedure to keep it clean, or do as the owner manual says:
"Drain, flush, and refill clutch hydraulic system at a
regular service interval (I or II) every two years. This
service can be complex; you should have your dealer/
retailer perform this service."

More related owner manual info here:
http://forums.corvetteforum.com/c6-z...post1572822007

Ranger

Thanks for that reminder, KGjevre.

In MD/DC/NoVa, dealers charge $175-$225 for bleeding the clutch. And unless the procedure is performed meticulously, the Chevy tech will get air in the hydraulics in the process. That will move the engagement point down near the floor, where most of us hate it to be.

Fortunately, the Protocol will disgorge the sequestered air in the hydraulics in about 20 minutes of work, without a return to the dealer.

Ranger

MtnBiker09Z

Yes, dirty fluid could do that over time, but that is NOT what people are using the frequent cleaning method for. They are mostly complaining about sticky or hanging clutch pedal. What you offer is nothing more than a placebo for this primary complaint. It may well do good over the long run under the conditions you describe in your many drag races.

I quote another: "Being the 2nd to 3rd gear shift with non pedal return ONLY happens at high RPMs says it is not a fluid issue.
The same fluid in hot weather in bumper to bumper traffic has never caused the problem which shows again it is not the fluid but the clutch pressure plate and slave design."

For the many vette owners that don't race this is a waste of money and time. They should just leave the fluid alone. But, hey, placebos do work, so have at it.

Ranger

Over the past ten years of working on this problem, I've helped one-to-one (phone, email, PM) more than a thousand owners across the country and overseas solve their clutch pedal issues. Mild-driving folks, street guys who drive aggressively, track racers, and drag strip hounds. At stock and near-stock power levels almost all the issues were cured. Were there an inherent irreconcilable design issue with the clutch itself, the remedies we follow would not work.

I'd point out too, some dealer techs hate any pedal remedy that obviates the (needless but) lucrative clutch swaps they most always recommend to any Corvette owner with pedal issues. That $2K bill to the guys out of warranty is sweet money to the tech and the dealer. And even in-warranty they still manage to rip GM for the unnecessary work.

So it should come as no surprise that a couple of the GM techs who post to the lesser-traveled forums would be screeding out solutions to pedal issues that involve (1) clutch swaps (2) full bleeds of the clutch hydraulics. Of course they never have time to read a laboratory report that sources much of the problem to clutch dust in the hydraulic fluid.

We live in such times. Got to squint with the eyes and the ears.

Ranger

ssspconcepts

I will stick to Ranger's protocol as the cost is a nominal $25/year and a little time. An ounce of prevention is worth a pound of cure.

Kutal

I just picked up a 04 not too long ago. Good thing I changed it before I drove it too much. Fluid was pitch black. Hmm... Previous owner babied it, but probably was not mechanically savvy. BTW you guys are great. I also did an oil change myself by browsing the DIY's. Other than the fact that I needed two oil filter wrenches....

Dirty Howie

2004 ????????????????


DH