View Full Version : Hard clutch pedal is due to overheating the fluid
needbigtruck
06-10-2002, 17:24
I've read a couple of messages on how the clutch pedal gets hard to push in after driving a long way without having to downshift, like on the open highway and your exit finally comes up. Well I had the same problem a few weeks back, My normal driving does not include a highway, so I didn't notice it. I took the truck to my local dealer thinking that we were going to have to go on a long ride for him to "expierence" it, but he looked for bullitens and then called tech assistance. They knew exactly what the problem is and how to solve it. Why they don't notify us I don't know. The problem is the brake fluid overheats between the master cylinder and the slave cylinder on long drives without using the clutch. It also causes the fluid to turn dark. The soulution is to wrap the line with heatshield tape and flush the old contaminated fluid out.I am having that done in the morning.
needbigtruck--let me know if that fixed the problem. Do they have a simple solution for the squecking clutch?
I was beginning to wonder it thats what was happening. Keep us posted on this, it may be time to get her in for her first service. :(
needbigtruck,
Is there any information the rest of use could use (service bulletin, flash...) that can help us explain to the dealership the problem and fix? Any "official" information would be great. Let us know if this solves the problem.
MaxRock
Amianthus
06-11-2002, 10:46
This is a new one for me. I've never heard of a clutch being able to over-heat the fluid. That DOT 4 stuff has such a high boiling point that is would all but impossible to overheat it in a clutch, IMO. Does it run in close proximity to the exhast? Close to anything with that much heat? Not to say it couldn't happen, but I've never heard of it.
needbigtruck--
what's the details?? any info to pass-on, spill the beans. :D :D
needbigtruck
06-14-2002, 07:21
Sorry the new living room floor, the computer has been OOS. Got the wrap on the 11th, and new fluid. I have no idea how they bleed the clutch. I won't be driving on a highway to test it until July 4th weekend. I will let you know how that is. Right now it seems fine. On the invoice they put "called TAC was informed to flush system and wrap with header tape. KO600 2.5 OG IE case #5657665". I don't know what all that means. Like I said I'll let you know after July 4th weekend. BTW i kind of agree with Amianthus, The line only comes within about 2 inches of the left exhaust manifold as it goes down to the clutch, can't see how this heats it up. But we'll see
Topic moved to 2500HD/3500 HD Trucks & Drivetrain Forum.
Turbo Al
06-15-2002, 10:48
Guys I think you/we have some misinformation here. To start with I do not have the 6 speed in my 2001 but I have the 5 speed in the 1993 and after 170,000 miles of driving it I can tell you that the clutch fluid does boil on the 1993 when towing up long hills BUT this results in TOTAL loss of clutch IE the pedal goes all the way to the floor and does NOTHING. Think about it if the fluid boils then you are pushing on AIR not Fluid.
I do not have an answer to what is causing the hard pedal condition, on the 1993 it was the pivot ball/clutch fork wearing out.
Turbo Al
needbigtruck
07-16-2002, 20:37
Thought I'd give an update. I bought a new traler in the 7500 lb. range and pulled it about 100 miles. The wrap did not work. The clutch still gets hard to push. Took it to dealer today and was told 3 things. 1.They had put DOT fluid instead of DOT4. Turns out they don't even have any DOT4 in the shop. Probably doesn't make that much of a difference. 2. They are going to replace the master, and slave cylinder. While they have it out they are going to wrap the line again. and Finally 3. Since I leave for Florida in 2 days, and the new parts won't get in for 3-4 days, they recommend not driving the truck to Florida. Imagine that, a $40,000 truck useless because the clutch fluid overheats. Well I am going. Can't cancel a family vacation. I'll just push the clutch in every 30-40 miles to keep cooler fluid in there. Hope we make it!
mackey_62
07-17-2002, 05:58
This thing is getting worse! :mad:
Pedal gets hard sometimes w/only about 20 miles of no shifting. Not towing either. Really hope this gets solved soon. Not willing to give up my truck for days at a time while dealer takes pot-shots at fixing problem. How can we get GM to look into this? So far it's only a nuiscance, but is this something internal in clutch that's going to get worse? Anyone have a pedal that gets so hard it barely goes in? Maybe a safety issue that would get more attention.
FirstDiesel
07-17-2002, 17:37
I find this clutch getting the fluid hot thing odd. I drive sports cars on the racetrack. We get the fluid HOT on the brakes. I can't see how the clutch fluid is getting so hot on a truck that it is giving you a problem. Want to prove it's not the fluid?? Invest 12 bucks and buy a can of fluid like ATE SuperBlue Racing Brake Fluid or ATE Type 200 Racing Brake Fluid. Same fluid but the SuperBlue is blue making it easier to know when the system is bled completely. This stuff has a boil point over 600 degrees and should not have any problem with any heat you have in the clutch system.
DieselsRule
07-17-2002, 21:49
Same problem with my truck. Why should I have to invest an additional $12.00 to make my truck work correctly for ATE SuperBlue Racing Brake Fluid or ATE Type 200 Racing Brake Fluid. It's GM's fault. First time the fluid was supposively changed (that's what the paper work says but it did not last but a mere day and now the problem is a lot worse. Any time the temp is above 85 and you drive the truck for more than 1/2 hour the problem sporadically occurs. I just know I want it fixed as I'm tired of trying to guess how much effort is needed to push in on the clutch.
FirstDiesel
07-18-2002, 04:36
You don't HAVE to spend 12 dollars for fluid. Yes, it's GM's fault. Want to try to get a truck that works right?? Or want to make GM do the right thing while you drive something with a problem and bitch about it?? JMHO, if it were me, I'd try some different fluid on my own and see if it helped.
Turbo Al
07-18-2002, 16:56
Inquiring minds want to know so SOMEONE change the fluid to the good stuff, I personally don't think it will help with the problem you guys are describing -- again it sounds like a mechanical problem and not the fluid. :( but if I keep the 1993 I will change it out -- thanks for the tip First Diesel.
[ 07-18-2002: Message edited by: Turbo Al ]</p>
FirstDiesel
07-18-2002, 19:47
Turbo Al
That's exactly my point. I don't beleive it's the fluid but changing to fluid like the ATE should make a noticeable change if the problem is really the fluid. If it makes no change your out 12 bucks and can tell the dealer to stuff it and find me a real fix.
If the fluid was expanding, wouldn't it just push on the slave cylinder instead of building up pressure? I don't have the manual transmission so I don't know how it works, but I can't see the problem being fluid expansion.
FirstDiesel
07-28-2002, 18:34
Neither can I, and that was the point of my idea of using some high quality racing fluid. If it still did it with that stuff you could have something to tell the dealer. Like your FOS! smile.gif
needbigtruck
07-30-2002, 02:32
Well Got back from Florida. I took DOT 4 with me and changed out the fluid in the reservior before I left and once more after I got to Florida. It was getting very hard to push in. Luckily I didn't listen to the dealer and not go on vacation, we had a good time and only after we got to Florida did I need to change the fluid. Once the new fluid is in it's fine for a while, but the fluid changes color very quickly (the dealer told me this is normal) and then it gets hard to push in again. I believe the slave cylinder is getting heated from the bearing. That is not enough to cause the problem, I believe we are getting moisture into the system (hence the color change). I took a close look at the cap when I changed the fluid in Florida and the plastic thing at the bottom of the rubber boot has a hloe in it allowing atmoshphere to come in contact with the brake fluid. I believe the moisture is getting into the fluid and that is what is boiling which would displace the brake fluid in the slave cylinder making the clutch hard to push in the first time after a long run without clutching. Now I just have to try and convince the dealer. I have suggested this to them before, because of the rapid color change, but they won't listen to me. Thanks for all your responses, hopefully we six speeders can get GM to fix this. I'm not sure I am going to let them tear my truck apart right now, not until they come up with a real answer.
This one is strange. I must assume that DOT and DOT4 fluid have the same properties of most fluids (excluding water and ammonia). If the fluid were to boil the result would be a very compressible compound. The pedal would not get hard to push, but rather very easy to push and probably wouldn't disengage the clutch.
Make sure you DO NOT put any type of racing or other fluid in the truck that does not meet the specs. in the Owners Manual. I don't know if the spec. is DOT4 or what, but if you put something in that's not to the manufactrers specs. you could void the warranty for that incident and they blame it on you.
The only thing I can think of that would cause the problem you describe is a mechanical problem due to heat expansion of the metal. That doesn't really make too much sense either since the clutch gets hotter when you use it rather than on long shiftless trips.
I would consider this a safety issue. Start a file with the BBB AutoLine immediately, and consider your state lemon law.
needbigtruck.
All brake fluid reservoirs are vented, the brake fluid is designed to resist moisture for a certain period of time. The color change in the brake fluid, I have never seen on any one of my cars including my race car. I do flush the fluid every 6 events or so, but never see any fluid color change.
I think GM may have a potential recall issue in their hands. Just keep on pushing the dealer, they will hopefully get it right soon.
If your area has a GM technical rep/supervisor, it may be worth it to have him ride along or drive, and experience the condition.
This is a safety issue, they should fix it.
Bora
FirstDiesel
07-30-2002, 17:15
I have 3 sportscars with fluid clutch systems. For some strange reason the same exact brake fluid used in the brakes and the clutch acts differently. I change the brake fluid and it stays the same color. I change the clutch fluid and within a week or 2 it darkens. I can assure you that does not stop the clutch from working. All 3 of my cars have dark clutch fluid and the clutches work fine.
Red Diesel
07-31-2002, 07:55
My truck goes in tommorrow morning for the same thing. I had the creaking problem and they changed the slave cyclinder. That worked to stop the creaking but the stiff pedal due to a long trip w/o shifting remains. I mentioned I have heard of others with the same problem and told him I heard it on a Bulletin Board. He smirked and said you can't rely on that. If the gods at GM don't acknowledge it then "it ain't so" or so they think. If anyone knows of a TSB from GM on this please let us know. I don't remember if the heat shield fix was a GM fix? I will let everyone know what I find out.
DieselsRule
07-31-2002, 11:48
My truck has been in once for the fluid change and it made the problem worse. Now it happens only after about a 25 minute drive when it is hot (above 85) or very humid outside. Been calling the dealer every couple of days telling them to make sure they have a fix before I bring it in again. GM Tech asked them to have me bring it in so they can tear it down to attempt to fix it. I'll drop it off Monday morning. It is a real pain when you get stuck in traffic and every time you put your foot on the clutch you get a different feel. My buddy has an 02 F**D with the same trans and he has yet to have this issue. Not that I would have a truck that sounds like a bucket of bolts rolling down a hill.
needbigtruck
07-31-2002, 23:19
DieselsRule I found out that after the dealer changed the fluid the first time, they used the brake fluid they had sitting around the shop. Turns out that was DOT 3. The cap says only use DOT 4. There probably isn't that much difference between the 2 but I found the same thing that the problem seemed to get worse. I put DOT 4 in, and it seemed to help a little. Go ask your dealer directly which fluid they used.
DieselsRule
08-06-2002, 21:55
Trucks been in the shop since Monday. Service dept call TECh and was told to order heat tape for exhaust pipe and to flush and replace fluid.
At least this time they are adding the tape. Any one get the tape and still have the problem?
needbigtruck
08-07-2002, 08:16
Dieselrule. They put heat tape on my clutch line, not on the exhaust. They also flushed (I found out later with DOT3 not DOT4 like it says plain as day on the top of the reservior). Neither one of these things helped. Hope it helps you. The dealer is going to replace my master and slave cylinder, if I call them and let them at my truck. Still thinking about that. Keep us updated on if yours is fixed.
DieselsRule
08-08-2002, 12:51
Picking it up today finally. 3 Days later the correct tape finally arrived. Wrong tape was shipped twice. Not sure when I can take it for a long drive to heat it up good but I'll let you know.
Forgot to add got lube job on intermediate shaft for steering rattle. Let's see if that works. Wonder why no bearing replacement yet although this is the first attempt here.
[ 08-08-2002: Message edited by: DieselsRule ]</p>
I have 8000 miles on my 2002 gmc and i have not had this problem. the only I have had is the noise pedal. I think the pedal and linkage ar really cheap. I can take my pedal and move side to side 2 1-2 to 3 inchs both ways
I'm not an automotive or hydraulic engineer, but I am still very skeptical that this is a fluid overheating problem.
I have no experience with this problem on a clutch, but I do know if your brake fluid boils the pedal goes to the floor... it doesn't get hard to push.
I suspect that this is a heat expansion problem with a metallic component.
New Theory on my part .
Though I haven't had the hard clutch problem personaly with over 52,000 miles , most of it long interstate runs , the truck is in the shop as we speak for it's third flywheel . 2nd replacement , 4th shipped , 2 came through damaged none available in North America . The one that came through in one piece Monday was from Canada . Have been waiting over a month .
Problem : noise in last inch to inch 1/2 of clutch travel .
Gm diagnosis : failing dual mass flywheel .
1st time @ 35,950 miles when transmission removed, bearing in center of flywheel had failed scoring input shaft , replaced flywheel and transmission .
Now it's mine , flywheel part of engine $100 deductable .
This bearing is pressed into the center of the flywheel and is permenently lubed . It only comes into play as the pedal is applied .
Could this be the problem with the others stiff clutch ??
Mac
mackey_62
08-11-2002, 18:34
spctr13,
You said last inch or so of travel?
Does it sound like a little chirp under the truck?
Maybe a chipmunk trapped in the bellhousing?
I've had the squeaky pedal, not talking about that. Actually haven't heard the pedal in awhile now that I think about it.
No, this chirp is definetly different. Not while depressing the pedal, only releasing it. If I could just find a volunteeer to hang under the truck while I run it thru some gears. Windows up, AC on I can't hear it, not real loud. I'd bet it's a metal/metal rubbing or no lube kind of thing though. Can't say it's directly related to the hard clutch, Little friggin chipmunk's there all the time. :mad:
No chipmunk !! Fairly loud ,especialy leaving toll booths between the barriers . Also can be heard by driver and anyone nearby while stopped ,in neutral, and depressing and releasing the clutch . Also downshifting at turns 4th to 3rd , 3rd to 2nd .
Mac
needbigtruck
10-31-2002, 19:09
Well I finally took my truck in to get the new parts put in. The dealer called and said if I didn't have the work done they would have to send the parts back and open a new work order on the problem. She also told me there was $1000.00 worth of parts, which included the master, slave cylinder and a gasket. I haven't gotten the work order yet they are mailing it to me. They took the whole xmission out, both drive shafts and the transfer case. That includes draining all the oil, so I got new xmission fluid also. The mechanic said my clutch looked fine, no cracks or anything else to suggest that something was wrong causing the hard pedal. He said GM tech told him some of the new slave cylinders might have been a little out of tolerence and were affected by heat. Since the slave cylinder is actually mounted to the throw out bearing it is exposed to the engine heat at the back of the engine. The clutch feels a little easier to me in general, unfourtunately I haven't had the problem since it got cold here so I am not sure when I will really test the new slave cylinder. Hope this sheds some light on an allready confusing issue. I still think GM is grasping at straws, they really don't know what is wrong and are just throwing new parts at the problem.
mackey_62
11-01-2002, 06:39
But this could be the fix???? right???
Even in the cold weather, I still got that friggin chipmunk trapped in there :mad:
needbigtruck
Thanks,keep us posted.
Here's my two cents. I have a ZF and I have been thinking about it. I think the hard pedal comes from the great amount of holding power the clutch must have. As it goes down the road for a while it just clamps tighter due to centrifical forces and then the first engagement of the clutch is just hard. After the first one it is easy again hot or cold. This explanation would be too easy!!
CPMac632
11-03-2002, 08:29
Now that I have added a lot of power to my truck I can roll along at 60mph and step on it and slip the clutch. Every time I make the clutch slip for a few seconds the pedal gets very stiff to depress for the first cycle and part of the second one but then it goes back to normal until I slip the clutch again.
Don't know if this has any bearing (pun) but there are times when I start the engine while in 2nd gear/clutch in and the truck wants to lurch forward. As if I didn't really push the clutch all the way in, which I did. Never any problems with the hard pedal you guys have.
Mike
Does anyone else have a chatter noise, through the shifter, when you step on it in 5th or 6th gear?
I have heard a chatter but only when I should be in a lower gear. I think this is normal. Old 1/2 ton Chevy did the same and I had the HD 5-spd in it.
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