Ranger

Here are a two pics by member Ian Black showing before and after a sequential flush of the fluid in the clutch master cylinder. Heat causes the stock DOT3 fluid to get black, gooey, and funky. Left like that, the particulate material clogs up the clutch hydraulics and causes pedal woes, including the dreaded sticking pedal syndrome. Two additional pics are below of a friend's reservoir after 5K miles without changing the clutch fluid. Nasty, huh? He was wondering why his clutch pedal was sticking.

Moral of the story is to regularly change the fluid in your clutch reservoir anytime it begins to take on color. I check mine every time I add gasoline and change the fluid when needed to keep it fresh, clear in color

By changing it regularly, I avoided pedal woes in 350 passes in my 2002 Z06. And am following the same routine in the C6Z.

EDIT: Clutch Fluid Changing Kit

Ranger

Cobra4B

Looks like a urine sample

I have a remote bleeder line, and when running HPDE's I use the turkey baster method to keep it clean too.

Really helps.

Ranger

While denying that heat was even an issue on the C5Z06 clutch pedal woes, Chevy is putting DOT4 brake fluid in the C6Z06 clutch hydraulics, but staying with DOT3 in the marque-car's brakes. That might reveal something about heat concerns in the clutch hydraulics. Actions speak louder than words.

Ranger

Richie Carbone

It's alot easier to just run DOT4. I used it in my 98 Z28 and even after 8 second burnouts on slicks and hot lapping the car I had no clutch issues at all.

C66 Racing

Those are some good shots Ranger. Like Brian, I now have an LAPD remote bleeder. In addition I use Wilwood EXP 600 Plus as my brake and clutch fluid and bleed it often in both. At some point in 2004 when my motor was out, I did replace the whole clutch assembly to try to ensure I didn't get the dreaded sticky clutch issue at an inopportune time. So far so good.

Bret01Z06

How hard is it to change. I got my Z06 used with 51K miles and I know it was beat on some. I want to change the clutch, brake, tranny and diff. fluids just so I know it's all good.

Ranger

"CLUTCH HYDRAULIC SYSTEM (condition) - is made up of a master cylinder hydraulically plumbed to a slave (actuator) cylinder. The hydraulic clutch fluid...is hydroscopic and over time it tends to absorb moisture indirectly from the atmosphere. The fluid reservoir features a vented twist-off cap enclosing a drop-in atmospheric moisture barrier type seal. The upside-down top-hat shaped barrier also acts as an atmospheric pressure equalization member responsible for reducing the tendency of gravity induced leakage of fluid from the system."

****

"A Common Problem with - the clutch hydraulic slave (actuator) cylinder is that they are susceptible to developing a hang up spot between the seal and the bore at the fully extended end of the cylinder's travel range.

This seal-hang-up condition normally develops when moisture is present in the hydraulic system and the vehicle is not in use for several days and/or weeks at a time. This hang up spot is usually caused by oxidation and/or contaminant build up causing a segment of the bore to have a higher seal to bore surface tension than the rest. It usually forms at the fully extended seal-to-bore contact point.

The hydraulic clutch system is a relatively low pressure system and does not exert enough barrel pressure to free the slave cylinder wall of this type of build up after it has developed.

The problem with this condition is that the clutch hydraulic system will bleed out normally but still have a hang up spot present. This condition creates a problematic operational situation in the system where even a full clutch pedal depression will not allow complete disengagement of the clutch for more than just a brief instance when the pedal is depressed and held to the floor.

The initial hydraulic fluid surge within the slave cylinder presses the actuation rod far enough for complete disengagement only to spring back slightly when pedal movement is halted in the fully depressed state. The spring back is caused by flex in the slave cylinder seal getting hung up and stretching a bit further only to return to its normal shape when surge pressure subsides.

This condition will mislead most technicians into believing that the clutch hydraulic system is operating at an acceptable level. Under these conditions, exactly timed quick shifts will occur fairly smoothly because the brief instance that the slave cylinder bore seal stretches is the same instant that the shift occurs. When the shift sequence is slowed down, the spring back of the slave cylinder occurs before the shift lever actuation causing a not-so-smooth gear engagement event. This causes the synchronizer to work much harder than necessary and is exposes the synchronizers and dogteeth to potential damage especially during higher RPM shifting."

Note: This explanation is from my clipping files. If I can find the original source, I'll edit it in.

Ranger

Ranger

I'd suggest checking the fluid every time you fill up with gas. Any time you see that the fluid is even slightly murky, then change it every few days until its remains clear. The reservoir holds about 3 oz., about 20% of the entire capacity of the clutch hydraulics. By doing this you are keeping the average freshness much higher and ridding the system of debris before it accumulates.

The procedure is:

(1) Draw out the funky fluid with the syringe. Picture of Syringe
(2) Wipe out the reservoir with a paper towel.
(3) Refill with fresh fluid to the fill-line.

That's it. Takes about three minutes. Take care to keep the (corrosive) fluid off your paint. I dispose of the spent fluid in a sealed container.

Some folks find this procedure too much trouble. But other that follow it avoid pedal issues that are MUCH more bothersome.

Ranger

bernrex

Thanks Ranger ... I'll check mine tonite for color.

Lawdogg

I remember GM telling us the change in color to the clutch fluid was normal and caused by a chemical reaction with some parts of the system. A little hint, next time you change out your clutch, take the throwout bearing apart. You will see at least part of the problem causing the sticky pedal.

Ranger

That's what they said. BUT their actions show concerns for heat: on the C6Z06 they are:

(1) loading DOT4 in the clutch hydraulics vice C5Z's DOT3.

(2) heat-shielding the lines for the clutch hydraulics, vice unshielded on the C5Z.

Ranger

bernrex

So ... would DOT4 work / be better ... for the C5 car?

Ranger

Hi bernrex,

On my 2002, I changes the fluid in the clutch master cylinder frequently enough that DOT3 was sufficient.

On my 2006, the DOT4 fluid changes color to dark and semi-opaque (particulate matter) after a few launches, even with the heat-shielding on the line.

If you have occasion, insulating the hydraulic line with "cool soxes" (normally used for plug wires) is a good idea.

Ranger

Blooty

Hey this is exactly what happened to my car...I thought it was the clutch. Anyhow, I drove it over the weekend...after I manually brought the clutch back up out of dreaded sticky mode. So, I will change the fluid but do you think I should take the car in and have them check it out to see if there is anything else wrong w/it? I wouldn't want to get stuck again.... Is there any particular fluid I should get? Gracias.

Ranger

Hi Rippied Z06.

When you get a moment, please tell us what you found when examining the throwout bearing.

TIA,

Ranger

Ranger

Been wondering about the disposition of your issue, Blooty.

Change the fluid and keep doing so every few days until it stays clear. Any DOT3 fluid should be fine. In my 2002 I used Prestone brand, available everywhere. The magic is in keeping it fresh by frequent changes.

I'd sure follow this approach for a couple weeks and see if it does the trick. If not, then take it in for the part swap cure.

Ranger

Lawdogg

I'm not a mechanic, but the mechanic that took mine apart showed me where the plastic and metal shaft had enough galling to create a hangup.

chiefDave

Great info as allways I do mine every Sat AM while I do my the rest of the car. I did change to Motul 600 and it does hold up better to the launches, ie no heat issues at all now. I did get it warm with DOT 3 once, but after a wrap on the line (plastic from auto store) and new fluid, it is solid.
Dave

Blooty

Thanks Ranger! What part swap? Where did you get that turkey baster? Mine is not a daily driver....but am so happy to have my toy back on the road!!

Ranger

A dealer will make $$ on your non-warranty repair. So you would expect them to advocate the replacement of all the clutch parts including the hydraulics. That is the recourse GM followed to cure the dreaded sticking pedal syndrome. But many of us avoided or cured the issue with regular changing of the fluid.

Draw out the funky fluid with a syringe like this one, available at Walmart and most auto part stores. Picture of Syringe

Ranger