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Checked mine, (2017 bought 6/2017, now has 7800 miles always garage kept) fluid level was low and the diaphragm on the cap was sucked down and covered with milky white residue and what looks like water droplets. The fluid in the bottom of the reservoir already looked sludgy but not milky. I’m going to clean the reservoir out, wipe off the cap, refill and repeat regularly. I think if you live in a area with high humidity you may need to do this more frequently. I’m not sure but I think as the clutch wears down the fluid level of the clutch reservoir gets lower, as does the brake fluid level goes down when the brake pads wear down.
Checked mine, (2017 bought 6/2017, now has 7800 miles always garage kept) fluid level was low and the diaphragm on the cap was sucked down and covered with milky white residue and what looks like water droplets. The fluid in the bottom of the reservoir already looked sludgy but not milky. I’m going to clean the reservoir out, wipe off the cap, refill and repeat regularly. I think if you live in a area with high humidity you may need to do this more frequently. I’m not sure but I think as the clutch wears down the fluid level of the clutch reservoir gets lower, as does the brake fluid level goes down when the brake pads wear down.
I bought mine in Feb 2017 in Detroit, drove home to Austin. In November I took the cap off and the cap was covered with white slime as well.
What I'm experiencing now is the fluid will get milky stuff in it like after one day and just get progressively worse. Obviously I can't do a full bleed each time I clean and refill but the dealer bled it recently and no change in behavior. : (
This is what mine looked like in Nov 2017 as mentioned above.
Mine had about 20% of that white smegma on it and that’s after 25 months. I’m down here in costal OC Cali, the humidity is usually low here. Looks like these systems don’t keep moisture out very well. Are you using a synthetic DOT 4 fluid (sorry I didn’t read though all of the posts).
Mine had about 20% of that white smegma on it and that’s after 25 months. I’m down here in costal OC Cali, the humidity is usually low here. Looks like these systems don’t keep moisture out very well. Are you using a synthetic DOT 4 fluid (sorry I didn’t read though all of the posts).
That white gunk was from the factory fill. Other pics in this thread are also GM fluid. (DOT4). I wonder if GM fluid is synthetic?!?!
That white gunk was from the factory fill. Other pics in this thread are also GM fluid. (DOT4). I wonder if GM fluid is synthetic?!?!
I doubt GM used synthetic, not sure if you can mix synthetic with non synthetic. It probably says on the bottle of synthetic. Not sure why they fill the brake system with DOT 3 and clutch with DOT 4.
Are still in warranty? Seems like it should be covered if you are.
Yeah, it's covered, just a PITA. The car just spent a month in the shop getting pilot bearing, torque tube, rear end and one of the shocks replaced. $11K bill for GM. Sucks having to go back as I told them about this at that point in time.
I doubt GM used synthetic, not sure if you can mix synthetic with non synthetic. It probably says on the bottle of synthetic. Not sure why they fill the brake system with DOT 3 and clutch with DOT 4.
All brake fluid is synthetic. Don't know why GM spec's DOT 3 for brakes and DOT 4 for clutch, but 3 has lower boiling point and less water absorption for what that's worth.
GM clutch fluid, I believe, is made by Pentosin which is a decent German product. I have never seen that "milky residue" on any other car brake or hydraulic fluid. Only similar residue was on the oil caps of air cooled Porsches due to moisture.
Somewhere there is a problem. Sadly I can not tell you where it is. However, do not use brake fluid that has been previously opened since brake fluid is hygroscopic and absorbs water. Usually the purpose of flushing these systems is to remove water contamination so always best to use fresh fluid from a previously sealed container.
GM clutch fluid, I believe, is made by Pentosin which is a decent German product - - do not use brake fluid that has been previously opened since brake fluid is hygroscopic and absorbs water. Usually the purpose of flushing these systems is to remove water contamination so always best to use fresh fluid from a previously sealed container.
That's the standard advice, however Pentosin advised me in writing that an open container should last "at least" a year or two.
Here we are more than 3 yrs later and I still have the issue with slime instantly showing up in my clutch fluid (after a simple ranger method). The dealer claimed to have done several vacuum flushes but I call B.S. because there is no way they got to the bleed valve in the amount of time I was in the waiting room.
They claim "there is a lubricant, maybe lithium grease" used in the assembly of the master cylinder and that is what it is. They literally suggest the ranger method and it will eventually work its way out. Well, that was like > 3 pints of fluid ago, and ZERO change.
I have Googled my a$$ off and cannot find one single picture of fluid that looks like this with slime in "suspension". If it were moisture or air you'd think I would have found other examples. I am totally baffled. I've attached a pic today after a ranger method and a spin around the block. You can see the slime just starting to form in suspension. Overnight it will settle to the bottom.
So, I'm about to bite the bullet and replace the master and do a proper bleed (uugghh) and see what happens. I cursed that bleed screw back in my C5 days and now I'm 20yrs older......haha.
2025 C8 Stingray of the Year Finalist - Unmodified
2024 C8 of the Year Finalist - Unmodified
My 1LT MN6 was manufactured 8/31/19 and I purchased it new on 10/17/19. The car is garaged, not driven in winter and has never been tracked. In July of 2020 at 2,800 miles I checked the clutch fluid and it looked like nasty cooking grease. I have no idea why or what GM filled it with. Never had another manual car with a reservoir that looked like this. I did the Ranger method using Prestone DOT 4 and have done it once a year ever since. It has remained clear and "normal" looking between procedures.
Some / Many Corvette owners are very aggressively proactive with their clutch fluid and very sensitive to abnormalities in it.
Chevrolet used to use opaque fluid reservoirs in the C5 and C6 and in the C7 switched to a solid black reservoir.
I have heard that most customer complaints centering around the clutch fluid are unwarranted and the vehicles function as designed. Dealers and GM see this as wasted time and unnecessary concern.
I wonder if GM switched the reservoir to solid black in an attempt to get owners to spend less time over analyzing the fluid within?
My 1LT MN6 was manufactured 8/31/19 and I purchased it new on 10/17/19. The car is garaged, not driven in winter and has never been tracked. In July of 2020 at 2,800 miles I checked the clutch fluid and it looked like nasty cooking grease. I have no idea why or what GM filled it with. Never had another manual car with a reservoir that looked like this. I did the Ranger method using Prestone DOT 4 and have done it once a year ever since. It has remained clear and "normal" looking between procedures.
interesting. Did it have that white slime in it as well?
wow some interesting looking fluid, does indeed look like grease of some sort.
mine was empty initially then dark after 30 pumps
then after a few more sessions much better looking and its keeping a nice level
ill open up another brake fluid bottle soon and repeat a few times
My 1LT MN6 was manufactured 8/31/19 and I purchased it new on 10/17/19. The car is garaged, not driven in winter and has never been tracked. In July of 2020 at 2,800 miles I checked the clutch fluid and it looked like nasty cooking grease. I have no idea why or what GM filled it with. Never had another manual car with a reservoir that looked like this. I did the Ranger method using Prestone DOT 4 and have done it once a year ever since. It has remained clear and "normal" looking between procedures.
You're in good company - the fluid in my '19 Z06 looked sinilar when I checked it at about 3500 miles earlier this year. I used the so-called "Ranger Method" to clean it up and top-off the reservoir. I later found this variation on the theme that works even better... Move over Ranger Method! DIY clutch fluid flush tool.
Originally Posted by TraceZ
Some observations I've made.
Some / Many Corvette owners are very aggressively proactive with their clutch fluid and very sensitive to abnormalities in it.
Chevrolet used to use opaque fluid reservoirs in the C5 and C6 and in the C7 switched to a solid black reservoir.
I have heard that most customer complaints centering around the clutch fluid are unwarranted and the vehicles function as designed. Dealers and GM see this as wasted time and unnecessary concern.
I wonder if GM switched the reservoir to solid black in an attempt to get owners to spend less time over analyzing the fluid within?
I tend to be what you might call "aggressively proactive" with the fluids in all my vehicles. It does NO harm to change them more often than "required." The same cannot necessarily be said erring in the other direction.
With all due respect, I disagree with what you've heard about "most customer complaints centering around the clutch fluid" being "unwarranted and the vehicles function as designed." I wasn't happy with my clutch until I discovered and remedied the nasty-looking and low clutch fluid with which my car was delivered. Once I removed and replaced it, the clutch felt totally different (i.e., better).
I understand earlier generation Corvettes had translucent reservoirs, and really wish mine was, rather than the opaque black to which Chevy switched. Your theory about why is as good as any I've heard, though I disagree with Chevy's "solution" to the "problem."
Last edited by NortonCO; Oct 25, 2021 at 10:54 AM.
2025 C8 Stingray of the Year Finalist - Unmodified
2024 C8 of the Year Finalist - Unmodified
Originally Posted by Torch-Red-Z06
interesting. Did it have that white slime in it as well?
No. The photos look worse than it actually was. When doing the Ranger method after 2-3 times of repeating the remove, refill, pump, repeat, the fluid cleared up and has been good ever since. I still check it and go through the procedure once a year.
I've read that the master and slave cylinders are packed with a considerable amount of assembly grease during manufacture and that grease is what ends up making the fluid look gross but is actually harmless.
Is it possible that leaving it alone is better for the components than changing it out and getting rid of the grease? Does the grease allow the fluid to feel spongy? I don't know.
Is it possible the grease inside the components at assembly time makes bleeding the system easier for the line-workers?
I change mine using the ranger method every couple thousand miles. I've done so on C5, C6 and C7 and never had a clutch problem.
