Strange brake problem. Help needed
06-18-2019, 06:43 PM
#1
Burning Brakes
Thread Starter
Strange brake problem. Help needed
While out for a short joy ride about 2 weeks ago I applied the brakes lightly from about 45MPH on dry pavement. The car swerved hard left and the steering wheel turned with it. Fortunately I was already in the left lane. No ABS skid light appeared.
I drove home and looked at the brake reservoir. To my amazement the fluid level was down to the top of the systems fluid isolation divider. First thing in the morning I drove it to the dealer (Stingray) about 45 minutes away. They got right on it and when they took a look at the brake reservoir it was back to normal full. They put the car in the air and looked everywhere for evidence of a leak (none found), they further researched the issue, called the mother ship, etc. to no avail. So I drove home.
The next week I took the ZR out for a run and when I got to the first stop sign I almost put myself into the window. Applying what used to be normal pedal displacement now resulted in a very hard stop. I checked the reservoir and it was normal. New destination = the dealer. I learned that was normal braking. Bullshart. Now there isn't an inch and a half of pedal travel between the resting pedal position and aggressive stopping. I took it to the dealer again only to learn this was normal but they didn't have another ZR available they could compare it to.
Has anyone experienced anything like this? Or have any ideas. The fact that the initial problem sucked most all the fluid out of the reservoir and held it is the part I don't understand unless there is a fluid accumulator somewhere in the anti-skid system.
Thanks for your help - Kev
I drove home and looked at the brake reservoir. To my amazement the fluid level was down to the top of the systems fluid isolation divider. First thing in the morning I drove it to the dealer (Stingray) about 45 minutes away. They got right on it and when they took a look at the brake reservoir it was back to normal full. They put the car in the air and looked everywhere for evidence of a leak (none found), they further researched the issue, called the mother ship, etc. to no avail. So I drove home.
The next week I took the ZR out for a run and when I got to the first stop sign I almost put myself into the window. Applying what used to be normal pedal displacement now resulted in a very hard stop. I checked the reservoir and it was normal. New destination = the dealer. I learned that was normal braking. Bullshart. Now there isn't an inch and a half of pedal travel between the resting pedal position and aggressive stopping. I took it to the dealer again only to learn this was normal but they didn't have another ZR available they could compare it to.
Has anyone experienced anything like this? Or have any ideas. The fact that the initial problem sucked most all the fluid out of the reservoir and held it is the part I don't understand unless there is a fluid accumulator somewhere in the anti-skid system.
Thanks for your help - Kev
Last edited by Repo Pilot; 06-18-2019 at 06:45 PM.
06-18-2019, 09:01 PM
#2
Racer
I would start using my pdr system to record every drive cycle then if it does it again you will have it on video along with brake pressure speed and g forces
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06-18-2019, 09:18 PM
#3
Le Mans Master
Member Since: Jul 2007
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St. Jude Donor '09-'10-'11-'12-'13-'14-'15-'16-'17,'22-'23
Kev,
I've never had the low fluid or swerving you mention but my brakes are really "touchy" or sensitive, much more than my previous C6 Z06 and ZR1. I'm still not really used to it and will occasionally give my passenger and myself a good jolt. I asked Ben H. about this way back and he said his were not that way. I can live with it but hope you discover the solution. I have not done the burnishing but never did on the other ZR1 either and it was fine.
I've never had the low fluid or swerving you mention but my brakes are really "touchy" or sensitive, much more than my previous C6 Z06 and ZR1. I'm still not really used to it and will occasionally give my passenger and myself a good jolt. I asked Ben H. about this way back and he said his were not that way. I can live with it but hope you discover the solution. I have not done the burnishing but never did on the other ZR1 either and it was fine.
Last edited by BearZ06; 06-18-2019 at 09:18 PM.
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Repo Pilot (06-18-2019)
06-18-2019, 09:22 PM
#4
Race Director
Member Since: Oct 2000
Location: Deal's Gap 2004 NCM Motorsports track supporter
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You might consider having them do a brake system flush that purges air from ABS module also. I don't know what they use now but we used to have to get a Tech 2 tool to actuate the module. I would hope they have a ZR1 specialist on board. There is a difference between GM master mechanic, corvette specialist and ZR1 specialist. It is my understanding that Freeland Chevy in Nashville has 2 ZR1 specialists. One just got back last week from ongoing training in Atlanta. I drive 100 miles for their service. Hope you get it resolved soon. 
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06-18-2019, 10:53 PM
#5
Burning Brakes
Thread Starter
Not a bad idea, but the problem is that they think it is "normal" and there has been no explanation as to where all that brake fluid went.
06-19-2019, 01:24 PM
#6
Race Director
I agree with using the PDR. Put the over lay in the track setting so you have both pedal imputs shown as well as gforces=for those hard turns.
I use mine every time I drive my car, in fact both of them, Z06 and ZR1. I don't want some dummy claiming I ran a red light or something dumb like that.
I use mine every time I drive my car, in fact both of them, Z06 and ZR1. I don't want some dummy claiming I ran a red light or something dumb like that.
06-19-2019, 06:11 PM
#7
Race Director
Symptoms sound a lot like an ABS/AH problem. 
Where fluid's going and then return, a genuine mystery.
'7 Zs are so new if issue's a build-wide problem, other reports will begin to trickle in.
Only then can GM brainbugs learn WTH's really causing it & provide a solution.
Where fluid's going and then return, a genuine mystery.
'7 Zs are so new if issue's a build-wide problem, other reports will begin to trickle in.
Only then can GM brainbugs learn WTH's really causing it & provide a solution.
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Repo Pilot (06-20-2019)
06-19-2019, 07:50 PM
#8
Racer
I once had a tps sensor go bad on my C6 ZR1and it caused the active handling to kick in ,but it also would not let you go in to the Ptm sub menus
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Repo Pilot (06-20-2019)
06-19-2019, 10:00 PM
#9
Race Director
try to get to a meet somewhere near you and go for a ride in another ZR and compare... i'm sure there are more than few within an hour of you. good luck with it... to me sounds like typical CCB performance..
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Repo Pilot (06-20-2019)
06-20-2019, 05:53 AM
#10
Burning Brakes
Thread Starter
Exactly - that is the piece of this adventure GM or the dealer has not provided an explanation for. Plus what I think was the uncommanded brake activation of the left front brake that caused the car to swerve.
06-20-2019, 06:00 AM
#11
Burning Brakes
Thread Starter
So far I have not met another ZR in Orlando but that was one of my first thoughts. The big mystery to me is where the fluid went, Watson. No one has an explanation to that piece of the puzzle.
06-20-2019, 09:58 AM
#12
Race Director
Why if this happens enough it'll prove an issue exists w/ more than just one (yours).
Multiple reports citing like symptom's a mandate to GM's engineers to get to it ID'g issue & providing a solution.
Forewarned is forearmed, knowing it's capable of going into the cornfield is an advantage.
You're 'on record' once w/ GM re this, every time henceforth it happens be at dealer so they're legally informed.
God forbid something happens causing a loss --of any kind, what happened is/was on record each time.
Ball's in GM's court then, just be careful & on your game if/when out.
G/L., keep this updated please.
06-20-2019, 10:35 PM
#13
Burning Brakes
Thread Starter
I talked to the service manager at the dealer today - a former C6 ZR1 owner. He was only casually aware of my issue but after chatting he wants to know where the fluid went too. We will see what he comes back with.
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Landru (06-21-2019)
06-25-2019, 01:21 PM
#14
Instructor
Hey Kevin,
Any updates for us...I have not had this issue...but would appreciate knowing the cause in case I do.
The good news is you have someone to blame if something was broken...never let anybody else drive your ZR1!!!
Jeff
Any updates for us...I have not had this issue...but would appreciate knowing the cause in case I do.
The good news is you have someone to blame if something was broken...never let anybody else drive your ZR1!!!
Jeff
06-25-2019, 01:50 PM
#15
Burning Brakes
Thread Starter
No news yet Jeff. I'm out on a repo that will keep me busy awhile.
My questions remain where did the fluid go and what could be causing the "hard" and very sensitive brake pedal.
It will be next week before I know if there are any further ideas from the department of rocket science.
.
Also this issue has nothing to do with my "demo drive" as it happened before the drive.
My questions remain where did the fluid go and what could be causing the "hard" and very sensitive brake pedal.
It will be next week before I know if there are any further ideas from the department of rocket science.
.
Also this issue has nothing to do with my "demo drive" as it happened before the drive.
Last edited by Repo Pilot; 06-25-2019 at 01:54 PM.
06-25-2019, 06:33 PM
#16
Burning Brakes
The ceramic brakes in my 17 Z06 exhibited similar behavior. It was almost like learning to brake all over again. Even after 14k miles, braking could be very sudden.
Not certain if this helps, just something I experienced that kinda mirror's yours.
Not certain if this helps, just something I experienced that kinda mirror's yours.
While out for a short joy ride about 2 weeks ago I applied the brakes lightly from about 45MPH on dry pavement. The car swerved hard left and the steering wheel turned with it. Fortunately I was already in the left lane. No ABS skid light appeared.
I drove home and looked at the brake reservoir. To my amazement the fluid level was down to the top of the systems fluid isolation divider. First thing in the morning I drove it to the dealer (Stingray) about 45 minutes away. They got right on it and when they took a look at the brake reservoir it was back to normal full. They put the car in the air and looked everywhere for evidence of a leak (none found), they further researched the issue, called the mother ship, etc. to no avail. So I drove home.
The next week I took the ZR out for a run and when I got to the first stop sign I almost put myself into the window. Applying what used to be normal pedal displacement now resulted in a very hard stop. I checked the reservoir and it was normal. New destination = the dealer. I learned that was normal braking. Bullshart. Now there isn't an inch and a half of pedal travel between the resting pedal position and aggressive stopping. I took it to the dealer again only to learn this was normal but they didn't have another ZR available they could compare it to.
Has anyone experienced anything like this? Or have any ideas. The fact that the initial problem sucked most all the fluid out of the reservoir and held it is the part I don't understand unless there is a fluid accumulator somewhere in the anti-skid system.
Thanks for your help - Kev
I drove home and looked at the brake reservoir. To my amazement the fluid level was down to the top of the systems fluid isolation divider. First thing in the morning I drove it to the dealer (Stingray) about 45 minutes away. They got right on it and when they took a look at the brake reservoir it was back to normal full. They put the car in the air and looked everywhere for evidence of a leak (none found), they further researched the issue, called the mother ship, etc. to no avail. So I drove home.
The next week I took the ZR out for a run and when I got to the first stop sign I almost put myself into the window. Applying what used to be normal pedal displacement now resulted in a very hard stop. I checked the reservoir and it was normal. New destination = the dealer. I learned that was normal braking. Bullshart. Now there isn't an inch and a half of pedal travel between the resting pedal position and aggressive stopping. I took it to the dealer again only to learn this was normal but they didn't have another ZR available they could compare it to.
Has anyone experienced anything like this? Or have any ideas. The fact that the initial problem sucked most all the fluid out of the reservoir and held it is the part I don't understand unless there is a fluid accumulator somewhere in the anti-skid system.
Thanks for your help - Kev
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Repo Pilot (06-29-2019)
06-26-2019, 07:48 PM
#18
Advanced
Not that is matters too much in regard to the missing fluid but are you running the stock brake fluid or a high-performance variant? I have about 1300 miles of track time with the HP fluid and I drive rarely on the street but have not experienced anything like this. Any noticeable difference when the brakes are hot versus cold?
06-26-2019, 07:52 PM
#19
Racer
Could it possibly be the hill start assist kicking in ? Is your car a m7 or auto,,just throwing different things out there
06-29-2019, 10:19 PM
#20
Burning Brakes
Thread Starter
Not that is matters too much in regard to the missing fluid but are you running the stock brake fluid or a high-performance variant? I have about 1300 miles of track time with the HP fluid and I drive rarely on the street but have not experienced anything like this. Any noticeable difference when the brakes are hot versus cold?