[Z06] mushy clutch pedal after hard driving
12-20-2010, 07:31 PM
#41
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I posted this same thing at another forum, and I was told this can also be caused from my longtubes which get really hot near the master cylinder, which can cause the master cylinder fluid to boil....
so I was told to get some hi temp brake fluid that's used for racing...
and will these high temp racing brake fluids cause any issues on a DD Z06?
lastly, what is a dry and what is a wet boiling point? differences?
Thanks!
It might be worth a shot before I spend money on a tick master at 300 bux plus install if these high temp fluids will do the job...
so I was told to get some hi temp brake fluid that's used for racing...
and will these high temp racing brake fluids cause any issues on a DD Z06?
lastly, what is a dry and what is a wet boiling point? differences?
Thanks!
It might be worth a shot before I spend money on a tick master at 300 bux plus install if these high temp fluids will do the job...
Prestone DOT4 boils at 510F when the fluid is dry and 311F when the fluid is "wet" (that means it contains 3% water).
If you keep the fluid clean, the fluid never is in the wet zone. So to boil and create vapor-lock, the temp would need to reach 510F, which it never will.
The issue for you is whether the seals in your master cylinder are toast from lack of maintenance by the previous owner. Only way to know is to keep swapping the fluid until it stays clean after a drive. I've given you that advice before.
So paying big$$ for "magic' brake fluid to use in your clutch is not money well-spent.
Ranger
Last edited by Ranger; 12-20-2010 at 08:49 PM.
12-20-2010, 08:33 PM
#42
AMP Racing
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2023 C5 of the Year Finalist - Modified
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St. Jude Donor '09-'10-'11-'12
I have to give Ranger some props here too.
I have stock hydraulics and a stock clutch. My car dyno'd 354 NA and I have not been on the dyno with the spray yet.
I have no where near the number of passes Ranger has - I'm only at 250 or so.
I have the benefit of a remote bleeder, so keeping my fluid clean is a bit easier. I used the baster and sucked it out for quite a while prior to installing the remote bleeder though, and it worked fine.
I, too, had pedal issues. I have no idea what the previous owner did to my car. Last year, I replaced my master and slave with new GM parts. and added the remote bleeder at that time. I bleed it after every 3-4 passes now.
Dirty fluid boils at a lower temp and then it loses it's ability to move the slave. 6000 rpm launches and 6500 rpm shifts create a lot of heat, and clutch dust. Keeping it clean is vital too successful passes on the drag strip.
I've had many 1.5xx 60' times and gone low 11s NA and in the 10 with the 100 shot.
Stock clutch and hydraulics are fine. I'd love to log my passes to see how close I am to Rangers "perfect shift" numbers.
I have stock hydraulics and a stock clutch. My car dyno'd 354 NA and I have not been on the dyno with the spray yet.
I have no where near the number of passes Ranger has - I'm only at 250 or so.
I have the benefit of a remote bleeder, so keeping my fluid clean is a bit easier. I used the baster and sucked it out for quite a while prior to installing the remote bleeder though, and it worked fine.
I, too, had pedal issues. I have no idea what the previous owner did to my car. Last year, I replaced my master and slave with new GM parts. and added the remote bleeder at that time. I bleed it after every 3-4 passes now.
Dirty fluid boils at a lower temp and then it loses it's ability to move the slave. 6000 rpm launches and 6500 rpm shifts create a lot of heat, and clutch dust. Keeping it clean is vital too successful passes on the drag strip.
I've had many 1.5xx 60' times and gone low 11s NA and in the 10 with the 100 shot.
Stock clutch and hydraulics are fine. I'd love to log my passes to see how close I am to Rangers "perfect shift" numbers.
12-21-2010, 12:03 AM
#43
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A fair number of generally clueless posters on that site.
Prestone DOT4 boils at 510F when the fluid is dry and 311F when the fluid is "wet" (that means it contains 3% water).
If you keep the fluid clean, the fluid never is in the wet zone. So to boil and create vapor-lock, the temp would need to reach 510F, which it never will.
The issue for you is whether the seals in your master cylinder are toast from lack of maintenance by the previous owner. Only way to know is to keep swapping the fluid until it stays clean after a drive. I've given you that advice before.
So paying big$$ for "magic' brake fluid to use in your clutch is not money well-spent.
Ranger
Prestone DOT4 boils at 510F when the fluid is dry and 311F when the fluid is "wet" (that means it contains 3% water).
If you keep the fluid clean, the fluid never is in the wet zone. So to boil and create vapor-lock, the temp would need to reach 510F, which it never will.
The issue for you is whether the seals in your master cylinder are toast from lack of maintenance by the previous owner. Only way to know is to keep swapping the fluid until it stays clean after a drive. I've given you that advice before.
So paying big$$ for "magic' brake fluid to use in your clutch is not money well-spent.
Ranger
12-21-2010, 01:13 AM
#44
Tech Contributor
Thanks for this moisture infusion question.
Assertions that removing the cap on the reservoir will rapidly corrupt the fluid with water are overdrawn. The reservoir contains about 33% of the entire fluid capacity of the system. Keeping the cap off for 60-120 seconds to swap in 33% new fluid will reduce water content, not increase it. And that is true for each successive swap.
I’ve done a series of experiments where, with an open hood, I left the cap off the reservoir for 36-hours on a hot, extremely humid day in an unconditioned garage. I then capped the reservoir and made repeated runs through the gears with 7K 1-2, 2-3 and 3-4 shifts. The hydraulics performed flawlessly. Moreover, the DOT4 brake fluid I use is kept capped when not in use; but a 12-ounce can is used up over a 30-60 day period of fluid swapping. That routine has never presented an issue of water corruption of the clutch fluid in my car through 773 drag strip passes.
So the process you are using seems consistent with excellent practices.
Ranger
Assertions that removing the cap on the reservoir will rapidly corrupt the fluid with water are overdrawn. The reservoir contains about 33% of the entire fluid capacity of the system. Keeping the cap off for 60-120 seconds to swap in 33% new fluid will reduce water content, not increase it. And that is true for each successive swap.
I’ve done a series of experiments where, with an open hood, I left the cap off the reservoir for 36-hours on a hot, extremely humid day in an unconditioned garage. I then capped the reservoir and made repeated runs through the gears with 7K 1-2, 2-3 and 3-4 shifts. The hydraulics performed flawlessly. Moreover, the DOT4 brake fluid I use is kept capped when not in use; but a 12-ounce can is used up over a 30-60 day period of fluid swapping. That routine has never presented an issue of water corruption of the clutch fluid in my car through 773 drag strip passes.
So the process you are using seems consistent with excellent practices.
Ranger
Thanks !
The reason I asked is because I used your method for a good 3 months straight and it really cleaned out my entire system.
I did this a few years ago. Lately I started to notice a clutch mushy feeling after a hard 1-2-3-4 shift. I checked my fluid and its perfectly clean. I always check it every couple months. I have again started to flush out the reservoir every time I drive the car and its getting better. Even CLEAN 2 year old fluid can cause this mushy feeling too I suppose... Thanks !
Toque
12-21-2010, 06:46 AM
#45
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Ranger
Thanks !
The reason I asked is because I used your method for a good 3 months straight and it really cleaned out my entire system. I did this a few years ago. Lately I started to notice a clutch mushy feeling after a hard 1-2-3-4 shift. I checked my fluid and its perfectly clean. I always check it every couple months. I have again started to flush out the reservoir every time I drive the car and its getting better. Even CLEAN 2 year old fluid can cause this mushy feeling too I suppose...
Thanks !
Toque
Thanks !
The reason I asked is because I used your method for a good 3 months straight and it really cleaned out my entire system.
I did this a few years ago. Lately I started to notice a clutch mushy feeling after a hard 1-2-3-4 shift. I checked my fluid and its perfectly clean. I always check it every couple months. I have again started to flush out the reservoir every time I drive the car and its getting better. Even CLEAN 2 year old fluid can cause this mushy feeling too I suppose... Thanks !
Toque
(1) clutch dust infusion from aggressive driving
(2) water infusion from heat-cool cycles
(3) proper clutch capacity for engine power
If you don't drive the car aggressively, clutch dust infusion is not much of a factor; and so clean fluid will tend to stay clear in color. But water will enter the fluid over time through heat-cool cycles. Water is colorless. GM specification (announced in late-summer 2007) is to change the clutch fluid with new DOT4 every 24-months to remove accumulated water.
Seems likely your clutch fluid has a water content that is excessive. So successive swaps of the reservoir with fresh DOT4 fluid intermixed with driving should bring back a normal clutch pedal.
Ranger
12-21-2010, 07:57 AM
#47
Tech Contributor
Keep in mind that there are three issues of concern.
(1) clutch dust infusion from aggressive driving
(2) water infusion from heat-cool cycles
(3) proper clutch capacity for engine power
If you don't drive the car aggressively, clutch dust infusion is not much of a factor; and so clean fluid will tend to stay clear in color. But water will enter the fluid over time through heat-cool cycles. Water is colorless. GM specification (announced in late-summer 2007) is to change the clutch fluid with new DOT4 every 24-months to remove accumulated water.
Seems likely your clutch fluid has a water content that is excessive. So successive swaps of the reservoir with fresh DOT4 fluid intermixed with driving should bring back a normal clutch pedal.
Ranger
(1) clutch dust infusion from aggressive driving
(2) water infusion from heat-cool cycles
(3) proper clutch capacity for engine power
If you don't drive the car aggressively, clutch dust infusion is not much of a factor; and so clean fluid will tend to stay clear in color. But water will enter the fluid over time through heat-cool cycles. Water is colorless. GM specification (announced in late-summer 2007) is to change the clutch fluid with new DOT4 every 24-months to remove accumulated water.
Seems likely your clutch fluid has a water content that is excessive. So successive swaps of the reservoir with fresh DOT4 fluid intermixed with driving should bring back a normal clutch pedal.
Ranger
That's what I was thinking, but glad you verified my thoughts. Your a big asset to the forum Ranger !
Thanks !
Toque
12-21-2010, 09:31 AM
#48
Former Vendor
What, specifically, do you mean by "shorter pedal"? BTW, I've got one of your masters, and haven't adjusted it from it's stock setting. It seems to engage (narrower) higher off the floor than the stock unit, and the pedal effort is higher, but I've also got a new twin-disc clutch, so that could also be a by-product. If I use the turnbuckle adjustment, will I be able to get the engagement point closer to the floor?
