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Sticking clutch pedal write-up

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Old 07-03-2007, 05:00 PM
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Talking Sticking clutch pedal write-up

The Problem

When driven aggressively, GM cars with manual transmissions have the problem of the clutch pedal sticking to the floor or other symptoms as a hard or soft pedal., slow to return or lazy pedal, stuck mid way pedal, or the classic its just stuck on the floor board. For anyone that has experienced any of these they know how annoying they can be. Its even more annoying trying to find the right fix for the problem. Unfortunately there is no definite answer to this problem every car is different. For some they just need to flush the fluid some the drill mod solves the problem. Others have to start replacing parts such as the clutch master or the slave cylinder.

Since this problem seems to be ever so growing in the ls1 community I have taken the time to put together a write up on the steps that should be taken to hopefully solver your problem and hopefully stop it from ever coming back.


So how do you stop my clutch pedal from sticking in the first place?


First lets start off with those that have not yet experienced this problem or have recently changed all there hydraulics and clutch. The number one most important thing is to keep your clutch fluid clean and fresh. Its cheap and easy insurance to keeping your pedal working properly. Gm recommends changing it every 100,000 miles. This is total crap I donít think there is any fluid that should be left in your car for 100,000 miles. No one has come up with a specific time frame to change your fluid so I would leave it up to your judgment. If your fluid is black its time to change it but it should be done way before it turns black. You should try to keep your fluid clean and fresh. The harder you are on the car the more frequent it should be changed. I personally recommend a full bleeding of the system if your fluid its dirty but once kept up with you can get away with just swap out the fluid in the reservoir but every once awhile you should still do a full bleed of the system.

You clutch fluid is plain old DOT 3 brake fluid. Most run just regular DOT 3 but DOT 4 will work as well and has a higher boiling point. We all know that brake fluid boils and when it does it essentially breaks down and does not work as it should. The same goes for your clutch fluid as it is brake fluid. One must remember that the slave is located inside the bell housing. That location puts clutch fluid in a very high heat, stress situation. Also the line from the master to the slave is in very close proximity to the exhaust often even closer when you have headers. When launching or high rpm shifting the fluid temperate rises dramatically over regular driving. These situations of increased friction are sufficient to boil clutch fluid. Once the brake fluid has been boiled it will emit a gas or steam which when compressed in a hydraulic system meant for fluid it will cause a malfunction in the system aka you clutch pedal sticking or acting different than normal. Again this is why your fluid needs to stay clear and clean to keep your pedal from sticking.


For more information of keeping your fluid clean click HERE

First step to solving the sticking clutch pedal is to bleed the hydraulics.

Having clean fluid and no air in the lines is your best bet to keeping everything operating the way it should.

On to the bleeding the system

One of the more difficult things about a T56 is accessing the bleeder screw. You cannot see it without a mirror, so you must rely on feel. If you are beneath the car and you are looking at the transmission where the master cylinder line connects to the slave cylinder, reach straight upward. At the very top of the transmission you will feel a hex-shaped rod about two inches in length. That is the bleeder screw, which comes directly from the slave cylinder.

To bleed the system, you will need a 7/16thĒ socket, thin-walled, in ľ drive. It would behoove you to use a few swivels and extensions. I also highly recommend taping the socket to the extension/swivel/etc. If for some reason you drop the socket, it will end up at the bottom of the bellhousing and you will have a hell of a time fishing it out.

If you plan to bleed traditionally, you will need two people. One under the car opening and tightening the bleeder screw, and another in the car operating the pedal.

If you are not squeamish about cutting into your car, you can make traditional bleeding a one man job. Underneath the car, do your best to put a dent in the transmission tunnel, straight across from the bleeder screw, with a punch. Get into the car and pull back the carpet around the pedals, and cut a small Ďaccess squareí so that you can also fold back the plastic, foam-lined piece beneath the carpet. Under that you will find the dent you made. With a 1Ē holesaw, cut a small part of the tunnel out. Now, with a 7/16Ē socket and a few extensions, you can reach the bleeder while being in the car! From here you can operate the pedal with your hand and use your other hand to tighten/loosen the screw. When you are done, simply put a piece of duct tape over the hole and recover with the carpet. It does not introduce any more noise into the cabinet.

Here is what the hole looks like (I had to drill mine a couple times to get it right




Different options for bleeding the system

Your best bet for learning how to bleed would be to search this forum. People have posted many different ways of removing air from the system, from using a traditional way, a Mity vac , etc. If you want to do it traditionally (whether by yourself or with help) it is very simple. The reservoir needs to be full of fluid the whole time, otherwise you will just continue to introduce more air into the system. With the bleeder closed, push the pedal to the floor. Open the bleeder (fluid and air will come out). Close the bleeder, release the pedal, bring it all the way back up. This process gets repeated until you have a firm clutch pedal. Donít panic Ė it can take up to 30 minutes to get it bled correctly.

The fluid that dribbles out will end up in the bottom of the bellhousing, and it will seep out that rectangular hole in the bottom and take care of itself. If you would like, you can spray some brake cleaner into the cavity to speed the process along.

A thank you goes out to keliente for the clutch bleeding section. So might recognize it for the manual trans faq thread. I borrowed it from her so thank you keliente.


Iíve changed my fluid but I still have a sticking clutch pedal.

The next step if it already hasnít been done is the drill mod.

What is the drill mod?

To sum it up, basically GM didnít think things through all the way when selecting the hydraulic lines for your T56. The steel braided line that plugs into the master cylinder has a tiny, tiny hole in it, which causes unnecessary restriction. During a quick, high-rpm shift, fluid cannot get where it needs to go fast enough, so basically it will feel like you are shifting without a clutch. It may be difficult or impossible to shift into 2nd or 3rd, and you may have some problems with the pedal itself.

When performing the drill mod, you remove the master cylinder, separate the line from the cylinder, and drill it out. To visit a site with full information and pictures, click HERE . It will be listed under the Transmission section, along with the adjustable master cylinder install (although you can do the drill mod without changing the master).

Another good idea when doing the drill mod is to wrap your hydraulic line with some kind of heat reflective tape.

Iíve changed the fluid and did the drill mod my pedal still sticks.

Next step is to replace your clutch master cylinder.


You can use the same site as the drill mod for an install write up. They used a McLeod adjustable master. Through my research the stock GM 01+ master is the best. Most that have tried adjustable masters end up switching back to stock. There is nothing wrong with an adjustable master but for many it can be tricky especially if you do not know how to properly adjust one. For all you 98 to 00 people it is recommended that you upgrade to the 01+ hydraulics. Although there have been no test done the general idea is that if you fluid in your master turns black rather quickly after flushing it your master is shot. Like I said there is no proof to this statement but it seems to be an ever more popular belief. Most masters come bench bleed and full of fluid. This does not mean you donít have to bleed the system once itís all put together. It is recommended that if you do the drill mod on the new line that you bench bleed the master. For a write-up on how to replace the master click HERE

Last edited by JonB; 08-14-2007 at 08:57 PM.
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Old 07-03-2007, 05:01 PM
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I’ve changed fluid did the drill mod and my master and the pedal still sticks.

Next it’s time to replace your slave cylinder.


The slave cylinder is what pushes on the fingers of the clutch to make it release. In the flawed part, when the clutch gets hot, the heat is transferred to the slave cylinder, causing the piston inside the slave to expand, and it binds in its bore, causing the clutch pedal not to be able to come back up.

At this point you have tried everything to avoid this. This is the hardest and most expensive part. Unfortunately to get to the slave the whole tranny has to be lowered. At this point it’s also a good idea to replace the whole clutch assembly, since you’re already in there. For a write up on removing tranny/clutch slave click HERE



To sum everything up.

It is very important to keep your fluid clean.

First step is to bleed the system it is important to have clean fluid and no air in the system.

Second step is the do the drill mod.

Third step is to replace the master cylinder.

Fourth step is to replace the slave cylinder.

Fifth step is to replace the clutch assembly(usually done at the same time as the slave cylinder).

Last edited by JonB; 10-15-2007 at 02:22 AM.
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Old 07-03-2007, 06:12 PM
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fantastic writeup !!!! hopefully less people will ask about this now bahahaha
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Old 07-03-2007, 06:25 PM
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Originally Posted by 01CaMMMaro
fantastic writeup !!!! hopefully less people will ask about this now bahahaha
That's what i'm hoping.
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Old 07-04-2007, 02:36 AM
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nice work

you can always add it to the FAQ if it dost get sticky
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Old 07-04-2007, 09:45 AM
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Originally Posted by studderin
nice work

you can always add it to the FAQ if it dost get sticky
Very true. This is such an abundant problem that I think it deserves its own sticky though.
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Old 07-06-2007, 04:19 PM
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To the top
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Old 07-15-2007, 11:57 PM
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We've got some new info as of 7/14/07 gm acknowledges degraded clutch fluid causes pedal woes.

Originally Posted by Ken Fichtner;1561070929
Document ID# 1982105

Subject: Intermittent Spongy Clutch Pedal Sticking To The Floor During Hard Acceleration And High RPM Shifts - keywords contaminate fluid hydraulic #PIP4145 - (06/04/2007)

Models: 2005-2007 Chevrolet Corvette, Corvette Z06 Equipped with a Tremec 6-speed Transmission RPO MM6, MZ6

--------------------------------------------------------------------------------

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
Some customers may comment about an intermittent spongy clutch pedal feel or clutch pedal sticking to the floor. This may be aggravated by aggressive driving and high clutch operating temperatures. Higher than expected levels of water in the clutch fluid greater than 2% may cause the clutch fluid to boil. The presence of water in the fluid lowers the boiling point significantly; when these conditions are present the driver may lose customary clutch pedal feel and performance.

Recommendation/Instructions:
If the above condition is intermittent flush the hydraulic system using DOT 4 fluid part number 88958860 (88901244 in Canada), prior to replacement of any mechanical or hydraulic components.

To eliminate the opportunity for moisture to enter the clutch hydraulic system.

The clutch fluid level inspection should be a VISUAL inspection only. Look through the transparent reservoir and observe the fluid level. Avoid removing the cap. Do not remove the cap just to top-off clutch fluid. Leave the system closed and sealed. During PDI inspection or routine servicing the cap should not be opened for just an inspection.
DOT 4 clutch fluid has a 2 week shelf life. Do not use fluid if container opening date is unknown or older than 2 weeks. Do not mix or re-use old fluid. Current service information already covers the issue of reuse.
To provide the best clutch operation, it is recommended that the owner change the clutch fluid every 2 calendar years. Please flush and replace the clutch fluid with P/N 88958860 (88901244 in Canada) or equivalent DOT 4.
The current service information and owners manual will be updated to reflect this information.

Note: If the concern is not intermittent, inspect clutch hydraulic system for leaks and repair as necessary after repairs are completed flush system with DOT 4 fluid part number 88958860 (88901244 in Canada).

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

Thanks to Ranger for coming across some more great info.
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Old 07-21-2007, 10:56 PM
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Originally Posted by JonB
The Problem

Iíve changed my fluid but I still have a sticking clutch pedal.

The next step if it already hasnít been done is the drill mod.

What is the drill mod?

To sum it up, basically GM didnít think things through all the way when selecting the hydraulic lines for your T56. The steel braided line that plugs into the master cylinder has a tiny, tiny hole in it, which causes unnecessary restriction. During a quick, high-rpm shift, fluid cannot get where it needs to go fast enough, so basically it will feel like you are shifting without a clutch. It may be difficult or impossible to shift into 2nd or 3rd, and you may have some problems with the pedal itself.

When performing the drill mod, you remove the master cylinder, separate the line from the cylinder, and drill it out. To visit a site with full information and pictures, click HERE . It will be listed under the Transmission section, along with the adjustable master cylinder install (although you can do the drill mod without changing the master).

Another good idea when doing the drill mod is to wrap your hydraulic line with some kind of heat reflective tape.

Iíve changed the fluid and did the drill mod my pedal still sticks.

Next step is to replace your clutch master cylinder.


You can use the same site as the drill mod for an install write up. They used a McLeod adjustable master. Through my research the stock GM 01+ master is the best. Most that have tried adjustable masters end up switching back to stock. For all you 98 to 00 people it is recommended that you upgrade to the 01+ hydraulics. Although there have been no test done the general idea is that if you fluid in your master turns black rather quickly after flushing it your master is shot. Like I said there is no proof to this statement but it seems to be an ever more popular belief. Most masters come bench bleed and full of fluid. This does not mean you donít have to bleed the system once itís all put together. It is recommended that if you do the drill mod on the new line that you bench bleed the master. For a write-up on how to replace the master click HERE
I already bled my clutch fluid on my car 2374987234 times already. As for the drill mod, I havent done it yet. Maybe you can give me some hints, as that site doesnt really give the detail im looking for. Will I have to remove the drivetrain to do this mod? or, is it possible to just remove the line from the master in the engine bay and drill it there? I thought it was something in the slave that had to be drilled?

Thanks,
Gio
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Old 07-22-2007, 12:42 AM
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I've replaced the slave, master, used synthetic valvoline fluid, and flushed many, many times. I pulled the clutch and the disk and PP seemed fine but I went ahead and replaced the disk with a ceramic button type. Its obviously time to replace the PP. I am still curious though what the exact problem is. I wonder if upon high RPM speed shifts, could the adjuster on the PP be shifting position or is it the fingers on the PP that are pushing the slave back too far as the RPM's increase? I suppose if I were a real glutton for punishment, I would remove the trans and fix the PP adjuster so it couldnt move anymore.
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Old 07-22-2007, 02:19 PM
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Good info, sticky this and half the threads started on this section will be cut in half.
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Old 07-22-2007, 05:53 PM
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Sticky!
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Old 07-22-2007, 06:20 PM
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i have been told its also a pp problem like stated by davess02 with the added rpm the pressure plate stays enguaged but the fingers are pulled away from the slave causing the pedal to stick....my clutch doesnt "slip" just gets stuck to the floor done all the replacements 02 slave and master has the drill mod and higher boiling point fluid wraped the line and it still does it time for a text clutch
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Old 07-22-2007, 08:28 PM
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Originally Posted by xtremejimmy
I already bled my clutch fluid on my car 2374987234 times already. As for the drill mod, I havent done it yet. Maybe you can give me some hints, as that site doesnt really give the detail im looking for. Will I have to remove the drivetrain to do this mod? or, is it possible to just remove the line from the master in the engine bay and drill it there? I thought it was something in the slave that had to be drilled?

Thanks,
Gio
Ok the drill mod itself is done on the line that connects from the master cylinder to the tranny(which then goes into the slave cylinder). Most will go ahead and remove the master to do this. I did just read the other day of someone just pushing out the pin where it connects to the master and just removing the line. Once you remove the master and line from the car then remove the line from the master. Then end by the master is the side with the restrition in it. You then take the drill bit and drill out the restriction. Its all very easy(well maybe not your first time). If you have any other question please ask.
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Old 07-22-2007, 08:43 PM
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Originally Posted by 98mysticZ
i have been told its also a pp problem like stated by davess02 with the added rpm the pressure plate stays enguaged but the fingers are pulled away from the slave causing the pedal to stick....my clutch doesnt "slip" just gets stuck to the floor done all the replacements 02 slave and master has the drill mod and higher boiling point fluid wraped the line and it still does it time for a text clutch
To be honest I am still learning alot about these trannies and hydrolic system but generaly its a hydrolic problem. I have heard of people replacing all the hydrolics and still have a problem. Some of the guys running aftermarket clutch setups have needed to use a shim to finally solve the pedal problem.
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Old 07-22-2007, 08:44 PM
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Originally Posted by Doomsday
Good info, sticky this and half the threads started on this section will be cut in half.
Thats why I made this write-up. I was so tired of seeing 5 thread a day started about sticking clutch pedal's.
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Old 07-22-2007, 09:32 PM
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again its a good write up... and i am using all "stock" parts ls6 clutch PP gm through out bearing 02 slave and master but still have a problem got alot worse after the rev limiter was changed and i got a cam
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Old 07-22-2007, 09:50 PM
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Originally Posted by 98mysticZ
again its a good write up... and i am using all "stock" parts ls6 clutch PP gm through out bearing 02 slave and master but still have a problem got alot worse after the rev limiter was changed and i got a cam

Is your clutch slipping at all. With your numbers almost 400rwhp your clutch is at its limit. I would look into a better clutch setup. The ls6 does't hold up well once you start modding these cars. The added stress on the clutch from the extra power can cause extra heat which in turn cause problems with the fluid/pedal. I've read alot of stuff on people pushing numbers around yours still running the ls6 and haveing pedal problem they replaced the clutch with a better one, replaced the hydrolics and the problem was fixed. The major problem with finding the correct fix for this problem is that there is no definet answer to the problem. Most people go in the order I listed but when they get to the slave they replace the clutch assembly as well so theres no telling if it was the clutch or the slave that fixed the problem.
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Old 07-22-2007, 11:58 PM
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yea i am gettin a text oz700 i belive it is.. then putting on another new slave just cause i am in there and rebleading everything i know i am at my limits heck it could be slipping but i cant tell yet just know if i shift under factory rev limiter it will do good alittle loss in pedal pressure but push it to 6500 and it sticks bad... hell sitting in a parking lot and push the pedal in and rev it up to about 6200 6300 and it will stick which is why i think its the pp but its all going to be changed and like i said before all the hydro's replaced with 02 stuff new from gm and did the drill mod and wrapped the line so lets only hope when i get the clutch my rear doesnt go agian haha... great write up though
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Old 07-23-2007, 07:58 PM
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i vote this to be a sticky my car experiences all those problems. I am going to try and do the fluid change and drill mod
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