Curious clutch pedal behavior
09-19-2021, 07:52 PM
#1
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Curious clutch pedal behavior
I came out to my car yesterday to find that my clutch pedal had collapsed. I've been pretty good at refreshing the fluid with the bulb baster method. Plenty of fluid still in the reservoir of a medium brown color, No ultra black sludge in the reservoir.. No gradual change in pedal position either. The day before it was good, but then yesterday down near the floor. I could still shift OK but the engagement position had now shifted way down. I tried pumping the pedal thinking maybe it was some sort of bleeding problem but it stayed down near the floor.
Bit of research here suggested that maybe the return spring had broken. I pulled the pedal up today and looked under the dash and it seems fine. It comes back up and stays when I work the pedal. Clutch seems OK, although I haven't done anything except move the car back and forth in the driveway.
50,000+ on a 2007 Z06, which has been nearly dead reliable. Because of that I almost never frequent the C6 general discussion so maybe this has been discussed but a quick search revealed nothing but the broken spring theory, which it doesn't seem I have. Is there something about the spring that makes me want to look deeper into that? Can't make much sense of this otherwise. Next up will have to be road testing.
Bit of research here suggested that maybe the return spring had broken. I pulled the pedal up today and looked under the dash and it seems fine. It comes back up and stays when I work the pedal. Clutch seems OK, although I haven't done anything except move the car back and forth in the driveway.
50,000+ on a 2007 Z06, which has been nearly dead reliable. Because of that I almost never frequent the C6 general discussion so maybe this has been discussed but a quick search revealed nothing but the broken spring theory, which it doesn't seem I have. Is there something about the spring that makes me want to look deeper into that? Can't make much sense of this otherwise. Next up will have to be road testing.
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ignatz (09-20-2021)
09-19-2021, 11:03 PM
#3
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I am not sure why in particular it would be the master cylinder, but I'm willing to listen to a reasonable explanation before I start fixing what I don't know is broken.
My thinking is, in operation returning the pedal, the pressure plate would be pushing back against the throwout bearing/slave cylinder with quite of bit of force. The hydraulic connection to the master if intact pushes back with an equal amount of force as was applied to disengage the clutch. Can the master hang up somehow? After all it is just a piston, not much mechanically to go wrong there. I have no known leaks and the fluid level is fine
I did find this a possibility on a Z06 forum: "Also the C6 clutch pedal return spring is weaker then the C5s and many owners swap theirs with a C5 spring."
My thinking is, in operation returning the pedal, the pressure plate would be pushing back against the throwout bearing/slave cylinder with quite of bit of force. The hydraulic connection to the master if intact pushes back with an equal amount of force as was applied to disengage the clutch. Can the master hang up somehow? After all it is just a piston, not much mechanically to go wrong there. I have no known leaks and the fluid level is fine
I did find this a possibility on a Z06 forum: "Also the C6 clutch pedal return spring is weaker then the C5s and many owners swap theirs with a C5 spring."
09-19-2021, 11:16 PM
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TSB 14717 - clutch master cylinder. GM had provided a 10 yr/120 mi extended coverage for this part. Your vehicle is beyond the coverage unfortunately. However, the updated mc, part # 19331709, is only $100 & you should be able to change it in about an hour.
Typical symptom is clutch pedal to the floor. The new mc comes pre-filled & requires Dot4 fluid.
https://static.nhtsa.gov/odi/tsbs/20...23488-9999.pdf
Typical symptom is clutch pedal to the floor. The new mc comes pre-filled & requires Dot4 fluid.
https://static.nhtsa.gov/odi/tsbs/20...23488-9999.pdf
Last edited by JABCAT; 09-19-2021 at 11:17 PM.
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ignatz (09-20-2021)
09-20-2021, 09:57 AM
#5
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Clutch return spring does not actually return the pedal, it only insures that the pedal is fully seated in the up position to insure the brake light switch is depressed. In fact, many guys change the C6 spring to a C5 spring which is a bit lighter feel. Your issue is the master cylinder. As said they're about $100 and you can put it in yourself. Google clutch master cylinder replacement C6 Corvette and you'll get several video's on how to do it. You've got to remove the left front wheel and wheel well dirt shield on the rear half of the opening. This exposes a rather small opening that you can look and work through to remove the clip that holds the two halves of the line together, one from the clutch itself and the other that goes up to the pedal assembly. It's tight but can be done. Remove the push rod from under the dash attached to the pedal, twist the master cylinder clockwise about a quarter turn the the whole thing wiggles out around the brake master. New one goes back in the reverse procedure, twist the master counter clock wise to lock it in, connect the push rod, connect the line. New master comes filled and no bleeding is necessary. Biggest problem is connecting the line through that small opening in the wheel well. I found that using a regular household hammer using the head end, handle up, and wedge it between the steering column and the steel line would allow me to use a big screw driver to press the two halves of the fitting together. Put the snap ring on first. This will all make sense when you see it. About an hour project. Good luck.
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ignatz (09-20-2021)
09-20-2021, 10:04 AM
#6
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Everytime i see this . Its mostly the cutch, i know one day it works and one day it doesn't. If u see no oil driping under slave cylinder thats good, but other people will verify. Im sure its not M/C no disrespect to who suggested.
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ignatz (09-20-2021)
09-20-2021, 12:28 PM
#7
Safety Car
It is possible that your slave cylinder could be going out. And possible it is the clutch. But considering you are in the 50K mileage range, those are not likely.
Most likely IS the master cylinder.
I did a clutch change on my 2011 GS about 2 years ago. Only part that was not changed in the system was the MC. Only a couple of days ago, the clutch pedal got stuck half-way to the floor and did not return. Wasn't a broken spring either since part of the clutch install procedure was removing the return spring. Likely is the MC.
Most likely IS the master cylinder.
I did a clutch change on my 2011 GS about 2 years ago. Only part that was not changed in the system was the MC. Only a couple of days ago, the clutch pedal got stuck half-way to the floor and did not return. Wasn't a broken spring either since part of the clutch install procedure was removing the return spring. Likely is the MC.
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ignatz (09-20-2021)
09-20-2021, 12:35 PM
#8
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i believe the problem is the seals in the master allow fluid to bleed by, and create pressure "behind" the actuator, which keeps the clutch disengaged....
i've had this happen to me, and yes, pulling the pedal up can get it to work for awhile, until the next event...
there is an ntsb recall saying the failure can occur during a clutch readjustment event.... this part has nothing to do with what type of fluid is in the master/slave (yes, it does also say unapproved fluids)
"Dealers are to replace the clutch master cylinder with a revised unit that is more robust against pressure pulses,"
https://static.nhtsa.gov/odi/tsbs/20...23488-9999.pdf
i've had this happen to me, and yes, pulling the pedal up can get it to work for awhile, until the next event...
there is an ntsb recall saying the failure can occur during a clutch readjustment event.... this part has nothing to do with what type of fluid is in the master/slave (yes, it does also say unapproved fluids)
"Dealers are to replace the clutch master cylinder with a revised unit that is more robust against pressure pulses,"
https://static.nhtsa.gov/odi/tsbs/20...23488-9999.pdf
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ignatz (09-20-2021)
09-20-2021, 01:02 PM
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A variety of responses here and I thank you all. Remember from my first post, I said I still had clutch functionality, it was way down low on the floor however which was alarming but not tow truck level disabling. I'll copy a tech bulletin down below, but what interests me about 'drewz06's' comment, is "until the next event". That differs a bit from the Service Bulletin which requires you to determine if the Master Cylinder ACTUALLY (added my emphasis there) needs replacement. Maybe that is a way to get the dealer off the hook a bit, I don't know, I'll have to chase what "actually" means to them. If this automatic adjustment happens fairly frequently then this would be an outlier, but if it takes a while to get to an adjustment cycle and this was the only one, than yes I think I do need another Master Cylinder.
What education I got new from this is that there is a mechanical arrangement of some sort that accommodates clutch wear (like automatic emergency brake adjustment I suppose) that results in "forward adjustment". Maybe some sort of ratcheting thing once wear is pronounced enough.
On my own, sorting through stuff on the internet, clearly I am not alone, as I found the following:
What education I got new from this is that there is a mechanical arrangement of some sort that accommodates clutch wear (like automatic emergency brake adjustment I suppose) that results in "forward adjustment". Maybe some sort of ratcheting thing once wear is pronounced enough.
On my own, sorting through stuff on the internet, clearly I am not alone, as I found the following:
Bulletin No.: 09-07-31-001 Date: Jan. 08, 2009
Concern: Low Clutch Pedal, Difficult to Shift (Inspect/Replace Clutch and Pressure Plate)
2005-2009 Chevrolet Corvette, Corvette Z06
Some customers may comment on a low clutch pedal. In some vehicles, the pedal may appear to operate very close to the floor. Customers may also have difficulty shifting.
2005-2009 Chevrolet Corvette, Corvette Z06
Some customers may comment on a low clutch pedal. In some vehicles, the pedal may appear to operate very close to the floor. Customers may also have difficulty shifting.
Cause - The low pedal concern may be the result of a clutch that has prematurely forward adjusted.
Correction - Important: BEFORE ANY PARTS ARE REPLACED, follow the procedure listed below. DO NOT remove the cover to inspect. Inspect the fluid level from the side of the reservoir. If additional fluid is required, use only DOT 4 fluid from an unopened container.
1. Inspect the clutch hydraulic system for damage and leaks. Repair as necessary.
2. With the engine off, the transmission placed in neutral and the parking brake applied, verify that the clutch reservoir is filled to the “fill line.”
3. If the pedal is on the floor, pull the pedal back to the full up stop and hold for one second. The fill port in the master cylinder is at the very top of the stroke. If the pedal is not fully returned to the top of the stroke, new fluid cannot enter the master cylinder from the reservoir.
4. Check the reservoir to ensure the fluid is still full.
5. Drive the vehicle to ensure proper clutch engagement.
2. With the engine off, the transmission placed in neutral and the parking brake applied, verify that the clutch reservoir is filled to the “fill line.”
3. If the pedal is on the floor, pull the pedal back to the full up stop and hold for one second. The fill port in the master cylinder is at the very top of the stroke. If the pedal is not fully returned to the top of the stroke, new fluid cannot enter the master cylinder from the reservoir.
4. Check the reservoir to ensure the fluid is still full.
5. Drive the vehicle to ensure proper clutch engagement.
Note: DO NOT use P/N 24246378 for vehicles with this condition. P/N 24246378 can be used for replacement only in cases where premature forward adjustment is NOT suspected. PLATE,CLU PRESS & DRVN(W/CVR)
6. If the cause of the customer’s concern hasn’t been determined, replace the clutch and pressure plate assembly with P/N 24248985. Refer to Clutch Assembly Replacement in SI.
The above implies that if pulling the pedal up fixes things, that's about the end of the dealer involvement. A little crazy about replacing the clutch and pressure plate a a fix, but this is dated 2009, so maybe they figured out later that the master cylinder was the culprit! Still worried about "until the next event". I'll have to search my literature to see if I got this notice and ignored it. Probably did.
Last edited by ignatz; 09-20-2021 at 01:04 PM.
09-20-2021, 04:50 PM
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A variety of responses here and I thank you all. Remember from my first post, I said I still had clutch functionality, it was way down low on the floor however which was alarming but not tow truck level disabling. I'll copy a tech bulletin down below, but what interests me about 'drewz06's' comment, is "until the next event". That differs a bit from the Service Bulletin which requires you to determine if the Master Cylinder ACTUALLY (added my emphasis there) needs replacement. Maybe that is a way to get the dealer off the hook a bit, I don't know, I'll have to chase what "actually" means to them. If this automatic adjustment happens fairly frequently then this would be an outlier, but if it takes a while to get to an adjustment cycle and this was the only one, than yes I think I do need another Master Cylinder.
What education I got new from this is that there is a mechanical arrangement of some sort that accommodates clutch wear (like automatic emergency brake adjustment I suppose) that results in "forward adjustment". Maybe some sort of ratcheting thing once wear is pronounced enough.
On my own, sorting through stuff on the internet, clearly I am not alone, as I found the following:
What education I got new from this is that there is a mechanical arrangement of some sort that accommodates clutch wear (like automatic emergency brake adjustment I suppose) that results in "forward adjustment". Maybe some sort of ratcheting thing once wear is pronounced enough.
On my own, sorting through stuff on the internet, clearly I am not alone, as I found the following:
Bulletin No.: 09-07-31-001 Date: Jan. 08, 2009
Concern: Low Clutch Pedal, Difficult to Shift (Inspect/Replace Clutch and Pressure Plate)
2005-2009 Chevrolet Corvette, Corvette Z06
Some customers may comment on a low clutch pedal. In some vehicles, the pedal may appear to operate very close to the floor. Customers may also have difficulty shifting.
2005-2009 Chevrolet Corvette, Corvette Z06
Some customers may comment on a low clutch pedal. In some vehicles, the pedal may appear to operate very close to the floor. Customers may also have difficulty shifting.
Cause - The low pedal concern may be the result of a clutch that has prematurely forward adjusted.
Correction - Important: BEFORE ANY PARTS ARE REPLACED, follow the procedure listed below. DO NOT remove the cover to inspect. Inspect the fluid level from the side of the reservoir. If additional fluid is required, use only DOT 4 fluid from an unopened container.
1. Inspect the clutch hydraulic system for damage and leaks. Repair as necessary.
2. With the engine off, the transmission placed in neutral and the parking brake applied, verify that the clutch reservoir is filled to the “fill line.”
3. If the pedal is on the floor, pull the pedal back to the full up stop and hold for one second. The fill port in the master cylinder is at the very top of the stroke. If the pedal is not fully returned to the top of the stroke, new fluid cannot enter the master cylinder from the reservoir.
4. Check the reservoir to ensure the fluid is still full.
5. Drive the vehicle to ensure proper clutch engagement.
2. With the engine off, the transmission placed in neutral and the parking brake applied, verify that the clutch reservoir is filled to the “fill line.”
3. If the pedal is on the floor, pull the pedal back to the full up stop and hold for one second. The fill port in the master cylinder is at the very top of the stroke. If the pedal is not fully returned to the top of the stroke, new fluid cannot enter the master cylinder from the reservoir.
4. Check the reservoir to ensure the fluid is still full.
5. Drive the vehicle to ensure proper clutch engagement.
Note: DO NOT use P/N 24246378 for vehicles with this condition. P/N 24246378 can be used for replacement only in cases where premature forward adjustment is NOT suspected. PLATE,CLU PRESS & DRVN(W/CVR)
6. If the cause of the customer’s concern hasn’t been determined, replace the clutch and pressure plate assembly with P/N 24248985. Refer to Clutch Assembly Replacement in SI.
The above implies that if pulling the pedal up fixes things, that's about the end of the dealer involvement. A little crazy about replacing the clutch and pressure plate a a fix, but this is dated 2009, so maybe they figured out later that the master cylinder was the culprit! Still worried about "until the next event". I'll have to search my literature to see if I got this notice and ignored it. Probably did.Last edited by JABCAT; 09-20-2021 at 04:51 PM.
09-20-2021, 06:13 PM
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The MC in my '12 GS was changed at 5k miles after doing exactly what you describe, and I changed the MC in my '11 Z06 at 17k miles for the exact same thing. Yes, it will work again, for a short time, if you pull the pedal up. But as was stated above, you'll have a "next event". I was thankful mine failed pulling out of my garage so I wasn't stranded on the side of the road anywhere. Because my Z06 is still covered under the extended coverage provided by the TSB I referenced above, GM reimbursed the cost of the part & sent me a check.
Sound like a MC change will be in the works for me, one way or another.
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JABCAT (09-20-2021)
09-20-2021, 08:02 PM
#12
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So here is a question. The Bulletin shows 2 part numbers: 19331709 and 19331708. How do you know which is the correct part number for your car? I have a 2011 Grand Sport and want to change my MC.
Edit: So I think that part number 19331709 is for LS9 cars and the 19331708 is for all others. Can someone confirm this?
Edit2: More searching, it looks like the revised part has a black reservoir which should be the 19331708 part. That is RockAuto is showing for the picture of that part.
Edit3: Even more searching. Seems like most people are using the 19331709 part. I am going to go with that one.
Edit: So I think that part number 19331709 is for LS9 cars and the 19331708 is for all others. Can someone confirm this?
Edit2: More searching, it looks like the revised part has a black reservoir which should be the 19331708 part. That is RockAuto is showing for the picture of that part.
Edit3: Even more searching. Seems like most people are using the 19331709 part. I am going to go with that one.
Last edited by Spaceme1117; 09-20-2021 at 08:26 PM.
09-20-2021, 08:14 PM
#13
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So here is a question. The Bulletin shows 2 part numbers: 19331709 and 19331708. How do you know which is the correct part number for your car? I have a 2011 Grand Sport and want to change my MC.
Edit: So I think that part number 19331709 is for LS9 cars and the 19331708 is for all others. Can someone confirm this?
Edit: So I think that part number 19331709 is for LS9 cars and the 19331708 is for all others. Can someone confirm this?
pull up pedal, mc acts like nothing happened...
09-20-2021, 09:11 PM
#14
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GMPartsGiant shows the 9 as appropriate for an LS2 and LS7 (me). I have a call in to my Service Department, if they can offer anything useful I will mention it. Time to look in my service manual to see if that is different from what was delivered originally. i.e. is the 9 more robust?
Last edited by ignatz; 09-20-2021 at 09:16 PM.
09-20-2021, 09:19 PM
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The dealership’s website from which I ordered listed part # 1709 as for the “supercharged” (ZR1). The parts department didn’t know of any differences between the two part numbers, so I ordered & installed the 1709 mc. Both part numbers come with black reservoirs and look identical.
09-22-2021, 06:34 AM
#16
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The dealership’s website from which I ordered listed part # 1709 as for the “supercharged” (ZR1). The parts department didn’t know of any differences between the two part numbers, so I ordered & installed the 1709 mc. Both part numbers come with black reservoirs and look identical.
09-22-2021, 10:49 AM
#17
Safety Car
GMPartsGiant shows the 9 as appropriate for an LS2 and LS7 (me). I have a call in to my Service Department, if they can offer anything useful I will mention it. Time to look in my service manual to see if that is different from what was delivered originally. i.e. is the 9 more robust?