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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / September 200693 Corvette Clutch issue
Please excuse the length of this topic. I am totally stumped and have tried just about everything I can think of to solve my problem (hence the length). I have a 93 Corvette with the ZF-6 manual transmission. The car is totally stock with 50K miles. I've owned it for 18 months. Right after I purchased the car I noticed the clutch pedal was difficult to depress and it didn't shift well. Two shops said I needed a new pressure plate. Last summer I changed the pressure plate, disk, throwout bearing and pilot bushing. It approved the shifting. However as I drive the car the clutch pedal stiffens up and the car does not shift as well. I've changed every possible part I can imagine. Here is a list: Clutch master (twice) Clutch slave (three times - did run into a manufactures defeat on two of the units) Braided clutch line Clutch pedal pivot bushings Throwout fork Pivot ball Pressure plate (twice) Clutch disk (twice) Throwout bearing (twice) Pilot bearing The throwout bearing guide tube is in great shape with no ridge or scuffing. I've literally been battling this problem for 18 months. I am totally stumped. Has anyone ever come across this scenario or does anyone have any advice? Thanks in advance for your help. Jim > Please excuse the length of this topic. I am totally stumped and have > tried just about everything I can think of to solve my problem (hence [quoted text clipped - 28 lines] > > Jim Try bleeding the system, with the car cold. Then wrap the line with header wrap. You may be boiling the fluid, causing bubbles,which don't compress good, and the clutch doesn't depress fully. Also use the highest temperature rated fluid you can get for that system.  SignatureSteve Walker fusion640@verizonwallet.net (remove wallet to reply) > I've changed every possible part I can imagine. Nope! I see you haven't mentioned having done anything with the pedal and its linkage. Your stiff pedal could be caused by something sticking in the pedal assembly itself. The shifting difficulty could also be attributed to a need for adjustment in the pedal. Let's see: tt's probably a blockage in the hydraulics, since you changed both cylinders and the line between them, right? It's probably not a problem with the clutch release mechanism including the pressure plate and disk, since all were serviced or replaced. What does that leave? Kaz Kylheku Wrote: > > I've changed every possible part I can imagine. > [quoted text clipped - 8 lines] > plate and disk, since all were serviced or replaced. What does that > leave? Boiling hydros will give you a mushy, ineffective pedal, not a difficult one.... I too though about the pedal linkage and pivot, I had a Chevy tow truck that had a very stiff clutch pedal action with questionable clutch disengagement, you had to toe it through the carpet to get it to disengage sometimes, and it seemed to get worse the farther you drove...after some adjustments failed to change anything signifigantly I noticed the clutch pedal pivot bar was actually moving around in it's bushings, negating pedal travel...had to disassemble it and replace the worn components... Signaturejeffcoslacker http://www.automotiveforums.com > Let's see: tt's probably a blockage in the hydraulics, since you Strange. Should read "it's probably not a ..." > > Let's see: tt's probably a blockage in the hydraulics, since you > > Strange. Should read "it's probably not a ..." Thanks for all the thoughts. In response to a few of the questions, you are correct I changed the master, slave and hydraulic line at least once. I also changed the plastic bushings located in the pedal pivot shaft (however the old ones looked good). I thought about air in the system or boiling fluid as well. However I thought that would lead to a spungy pedal instead of a stiff one. Have you ever run into the opposite situation where the hot fluid actually enlarges the seals and makes the pedal stiffer? I'm also wondering if the driver's side CAT is running hot for some reason and thus causing excessive heat by the line and/or slave? The car runs great at about 195 degrees. I've been using the GM hydraulic fluid since it contains some additives for the seals. I am stumped. Jim Jim Wrote: > . Have you ever run into the > opposite situation where the hot fluid actually enlarges the seals and > makes the pedal stiffer? > Jim I won't say it couldn't happen, but I've seen brake hydros so overheated from dragging linings and seized components that fluid actually exploded out of the resevoir when the cap was opened, and they just had no pedal (on the floor) Signaturejeffcoslacker http://www.automotiveforums.com >>> Let's see: tt's probably a blockage in the hydraulics, since you >> Strange. Should read "it's probably not a ..." [quoted text clipped - 15 lines] > > Jim My understanding was that it shifted hard, not caused the clutch pedal to get stiffer. My mistake. SignatureSteve Walker fusion640@verizonwallet.net (remove wallet to reply) I'm really having a problem with both the pedal getting stiff and it not shifting as well. It seems to act exactly the opposite of common logic. It shifts the best after the car sits for a weekend and the pedal is the easiest to depress. As I drive the car I find the pedal tends to stiffen up. It's not a huge amount, but it is noticeable. If the fluid is boiling I could see it not shifting as well, but I would think the pedal would get easier to depress because it's getting spongy. On the other hand if my stiff pedal problem was related to the clutch pedal linkage, I wouldn't think it would change the shifting only how hard it is to depress. I did try the Valvoline Synthetic brake fluid, but went back to the GM clutch fluid because of the lubricating additives. >> I've changed every possible part I can imagine. > [quoted text clipped - 8 lines] > plate and disk, since all were serviced or replaced. What does that > leave? FWIW, the 84 Fieros had an aluminum pedal assembly that was prone to bending over time... are there any recalls/TSB's on 93 Vette clutch pedals? However, I'm not suggesting you ignore the advice to insulate the lines from the exhaust heat, sounds like an excellent idea to me...some DOT 4 synthetic fluid will work nicely, and resist boiling/moisture breakdown. Don't use DOT 5, you have to flush the system several times with denatured alcohol before installing, and it doesn't mix with other DOT fluid types, so has to be kept DOT 5 or there will be trouble if contamination occurs. DOT 4 is the best thing since sliced bread, brake fluid wise... Signaturejeffcoslacker http://www.automotiveforums.com |
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