Clutch pedal will not disengage transmission - update - fixed!!!!
09-26-2010, 01:34 PM
#1
Rennlist Member
Thread Starter
Clutch pedal will not disengage transmission - update - fixed!!!!
I did a search and found a ton of information (too much perhaps).
What has been done:
1. new blue hose and flex clutch hyd line.
2. rebuilt both clutch master and slave cyl's.
3. bench bled system before reinstall (all lines and componenets connected).
4. reinstalled clutch hydrualics system.
5. removed and replaced brake master cyl, brake / clutch reservoir (new grommets between tank and brake master) and flushed out and bleed brake lines.
PO claimed car drove and shifted well until the clutch brake line blew which is when I bought the car.
With system reinstalled the clutch pedal seems to operate normally (seems firm but what do I know as this is my first 928).
Problem is the car will not go into gear with engine running (grinds when trying to push into gear) and when I put into gear before starting engine and attempt to start with clutch pedal depressed the car lurches under the starter indicating the clutch is not released.
I did bench bleed the assembly before install and have not tried to bleed more since finding the issue. Plan is to put the power bleeder on it and bleed at the slave and then observe through the inspection hole at the bottom of the bell housing to ensure the slave rod is moving.
I have never worked on a manual transmission / clutch system so if the bleeding does not solve the issue the adventure will be on.
Any other tips / hints?
Thanks
What has been done:
1. new blue hose and flex clutch hyd line.
2. rebuilt both clutch master and slave cyl's.
3. bench bled system before reinstall (all lines and componenets connected).
4. reinstalled clutch hydrualics system.
5. removed and replaced brake master cyl, brake / clutch reservoir (new grommets between tank and brake master) and flushed out and bleed brake lines.
PO claimed car drove and shifted well until the clutch brake line blew which is when I bought the car.
With system reinstalled the clutch pedal seems to operate normally (seems firm but what do I know as this is my first 928).
Problem is the car will not go into gear with engine running (grinds when trying to push into gear) and when I put into gear before starting engine and attempt to start with clutch pedal depressed the car lurches under the starter indicating the clutch is not released.
I did bench bleed the assembly before install and have not tried to bleed more since finding the issue. Plan is to put the power bleeder on it and bleed at the slave and then observe through the inspection hole at the bottom of the bell housing to ensure the slave rod is moving.
I have never worked on a manual transmission / clutch system so if the bleeding does not solve the issue the adventure will be on.
Any other tips / hints?
Thanks
Last edited by jwillman; 10-23-2010 at 03:41 PM.
09-26-2010, 01:53 PM
#2
Rennlist Member
Have you checked the release arm pivot bushing? If it was worn, you may have excaserbated it's wear w/new clutch hydraulics. Or it could popped off the pivot ball, located at the right top side of the bell housing... visible w/airbox removed.
09-26-2010, 02:35 PM
#4
Three Wheelin'
Even though you dealt with hydraulics, I'd still suspect the disc adjustment as most likely to act like that.
The master cylinder can be nearly impossible to get air out the first time but you should be able to tell if that were the problem.
Do you know how to do the adjustment on the little 'tabs'?
The master cylinder can be nearly impossible to get air out the first time but you should be able to tell if that were the problem.
Do you know how to do the adjustment on the little 'tabs'?
09-26-2010, 03:40 PM
#5
Rennlist Member
Thread Starter
Even though you dealt with hydraulics, I'd still suspect the disc adjustment as most likely to act like that.
The master cylinder can be nearly impossible to get air out the first time but you should be able to tell if that were the problem.
Do you know how to do the adjustment on the little 'tabs'?
The master cylinder can be nearly impossible to get air out the first time but you should be able to tell if that were the problem.
Do you know how to do the adjustment on the little 'tabs'?
What symptoms would I see if I had air in the system causing the issue?As far as the adjustment goes I have the shop manual and have looked at it but agian this will be my first time inside a clutch! Should be fun!
09-26-2010, 03:54 PM
#6
Three Wheelin'
I believe it would be more akin to all or nothing if you had air. A clutch disc dragging would consistanly act like what you experience with only a slight effect creating grinding at a standstill. I would bet on disc drag.
09-26-2010, 03:58 PM
#7
Rennlist Member
Did you preload the clutch MC rod?
I can't remember the exact spec, but goes something like: adjust the actuator rod until it's snug in the MC rod pocket, then backoff 1/4 - 1/2 turn (?).
At static, if the rod is pushing in the cylinder, it will bypass an oil passage and the MC won't function.
I can't remember the exact spec, but goes something like: adjust the actuator rod until it's snug in the MC rod pocket, then backoff 1/4 - 1/2 turn (?).
At static, if the rod is pushing in the cylinder, it will bypass an oil passage and the MC won't function.
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09-26-2010, 04:56 PM
#8
Rennlist Member
Thread Starter
So bled the system again and pedal if firm through full travel but still grinding with trying to get into gear. I got my helper back and with my son depressing the clutch pedal I can see movement at the release pivot point at the top rear of the engine.
I went under the car and I can see through the inspection hole that the slave cyl rod is traveling what I would guess to be around an inch so it seems to me that it isn't the hydrualics. The WSM shows operating travel at 17.4mm (5/8's in +) so it seems it is travleing far enough, correct?
I went under the car and I can see through the inspection hole that the slave cyl rod is traveling what I would guess to be around an inch so it seems to me that it isn't the hydrualics. The WSM shows operating travel at 17.4mm (5/8's in +) so it seems it is travleing far enough, correct?
09-26-2010, 06:34 PM
#9
Addict
Rennlist Member
Rennlist Member
Just a thought - how long since the clutch was last disengaged ? Could be that the flywheel/int plate/pressure plate have rusted to the friction discs.
Easiest way to fix this is to put car in gear, foot on clutch other foot on brake (hard if you don't want the car to move) then start the engine this is normally enough to shock the rust free.
Easiest way to fix this is to put car in gear, foot on clutch other foot on brake (hard if you don't want the car to move) then start the engine this is normally enough to shock the rust free.
09-26-2010, 06:49 PM
#10
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I had a heck of a time trying to bleed the clutch on the black widow. spent days on it ! I tried Clint at EG racing tried John tried none of us were able to bleed the clutch hydraulic system so the clutch completely Disengaged. We replaced evey thing blue hose clutch master and slave 2 times each and the hoses in between.
After careful observation and much debate we decided the system WAS completely bleed. The instant the clutch was depressed the smallest amount the the slave cylinder rod mover the same amt. we finally decided that the master cylinder was just not sized correctly to give the slave enough stroke to disengage the clutch completely. Said differently either the clutch master cylinder was too small or the slave was too big.
This led us to disassemble one of the clutch masters we had laying around and we found that the spool in the clutch master cylinder was machined with a stopper on the end wich limitted its stroke. So we machined 1/4" off the stopper and reassembled every thing and now the clutch works perfectly.
I would not suggest trying this until you have exhausted all other possibilities and make sue the slave cylinder rod is moving the instant you push on the clutch pedal.
I will try and find a couple of pictures to show the parts I am talking about.
After careful observation and much debate we decided the system WAS completely bleed. The instant the clutch was depressed the smallest amount the the slave cylinder rod mover the same amt. we finally decided that the master cylinder was just not sized correctly to give the slave enough stroke to disengage the clutch completely. Said differently either the clutch master cylinder was too small or the slave was too big.
This led us to disassemble one of the clutch masters we had laying around and we found that the spool in the clutch master cylinder was machined with a stopper on the end wich limitted its stroke. So we machined 1/4" off the stopper and reassembled every thing and now the clutch works perfectly.
I would not suggest trying this until you have exhausted all other possibilities and make sue the slave cylinder rod is moving the instant you push on the clutch pedal.
I will try and find a couple of pictures to show the parts I am talking about.
09-26-2010, 07:01 PM
#11
Rennlist Member
Thread Starter
Just a thought - how long since the clutch was last disengaged ? Could be that the flywheel/int plate/pressure plate have rusted to the friction discs.
Easiest way to fix this is to put car in gear, foot on clutch other foot on brake (hard if you don't want the car to move) then start the engine this is normally enough to shock the rust free.
Easiest way to fix this is to put car in gear, foot on clutch other foot on brake (hard if you don't want the car to move) then start the engine this is normally enough to shock the rust free.
I had done this yesterday while I was troubeshooting. I put the car in gear, held in clutch and foot brake with parking brake set. I attempted to start the car and it lurched so I confirmed the clutch was not released. Did not seem to free up anything and I was concerend about creating new problems by doing it again.
09-26-2010, 08:54 PM
#12
Team Owner
lets go back to the bushing on the top of the release arm with the aircleaner off and the clutch released can you move the arm on the ball??
any front to rear play??
the plastic bushing fits over the ball then the arm is pressed onto the bushing. if the bushing has failed then the arm will have too much play.
Next is the fact of different MC pistons...
the replacement piston has a tip on its end that will limit the travel,
this means that no matter how much you press the piston it will only move so much, if the MC has been replaced then there is a great chance the new part will not work.
Solution is to remove about 4 to 5 mm of tip BUT before you do you must measure the bore depth as you dont want the rear piston seal to go past the feed port, you may have an easier time working the problem on the bench,
ALSO you must check that the return spring can be compressed fully with some room to spare.
OR the spring will fracture and then small pieces of spring steel will cut your new seals to shreds,
solution remove as many winds as needed to allow the spring to compress with a bit to go before full compression, this could be cutting off a one or two winds
any front to rear play??
the plastic bushing fits over the ball then the arm is pressed onto the bushing. if the bushing has failed then the arm will have too much play.
Next is the fact of different MC pistons...
the replacement piston has a tip on its end that will limit the travel,
this means that no matter how much you press the piston it will only move so much, if the MC has been replaced then there is a great chance the new part will not work.
Solution is to remove about 4 to 5 mm of tip BUT before you do you must measure the bore depth as you dont want the rear piston seal to go past the feed port, you may have an easier time working the problem on the bench,
ALSO you must check that the return spring can be compressed fully with some room to spare.
OR the spring will fracture and then small pieces of spring steel will cut your new seals to shreds,
solution remove as many winds as needed to allow the spring to compress with a bit to go before full compression, this could be cutting off a one or two winds
09-26-2010, 09:45 PM
#13
Rennlist Member
If you have a '79, and the ball stud for the release arm was not updated ..... there is an excellent chance that it is broken: it may appear to be in place, but if the teflon ball cup in the release arm has degraded, the release arm works against the ball stud and it snaps - it has no place to go, so may still appear attached.
Take the air cleaner assembly off, and put a pry bar into that ~20x40mm rectangle on the top of the upper bell housing .... and gently try to push the release lever back. If all is OK, nothing will move, and the full ~25mm diameter rim of the ball cup will be visible: if not ..... there is an update for the ball stud with a M10 vs the early M8 thread - that is prone to failure!
All that is required is to drop the exhaust, lower bell housing, clutch, and then slide the transmission & torque tube back to remove the upper bellhousing. one then drills & taps the latter for the update - piece of cake.
Short version - read this thread, and have seen this issue previously: easy to confirm yea or nay. Show us a good pic of the top opening, or do the test above> if broken, easy to talk you through any detail required.
Take the air cleaner assembly off, and put a pry bar into that ~20x40mm rectangle on the top of the upper bell housing .... and gently try to push the release lever back. If all is OK, nothing will move, and the full ~25mm diameter rim of the ball cup will be visible: if not ..... there is an update for the ball stud with a M10 vs the early M8 thread - that is prone to failure!
All that is required is to drop the exhaust, lower bell housing, clutch, and then slide the transmission & torque tube back to remove the upper bellhousing. one then drills & taps the latter for the update - piece of cake.
Short version - read this thread, and have seen this issue previously: easy to confirm yea or nay. Show us a good pic of the top opening, or do the test above> if broken, easy to talk you through any detail required.
09-26-2010, 11:28 PM
#14
Rennlist Member
Thread Starter
lets go back to the bushing on the top of the release arm with the aircleaner off and the clutch released can you move the arm on the ball??
any front to rear play??
the plastic bushing fits over the ball then the arm is pressed onto the bushing. if the bushing has failed then the arm will have too much play.
Next is the fact of different MC pistons...
the replacement piston has a tip on its end that will limit the travel,
this means that no matter how much you press the piston it will only move so much, if the MC has been replaced then there is a great chance the new part will not work.
Solution is to remove about 4 to 5 mm of tip BUT before you do you must measure the bore depth as you dont want the rear piston seal to go past the feed port, you may have an easier time working the problem on the bench,
ALSO you must check that the return spring can be compressed fully with some room to spare.
OR the spring will fracture and then small pieces of spring steel will cut your new seals to shreds,
solution remove as many winds as needed to allow the spring to compress with a bit to go before full compression, this could be cutting off a one or two winds
any front to rear play??
the plastic bushing fits over the ball then the arm is pressed onto the bushing. if the bushing has failed then the arm will have too much play.
Next is the fact of different MC pistons...
the replacement piston has a tip on its end that will limit the travel,
this means that no matter how much you press the piston it will only move so much, if the MC has been replaced then there is a great chance the new part will not work.
Solution is to remove about 4 to 5 mm of tip BUT before you do you must measure the bore depth as you dont want the rear piston seal to go past the feed port, you may have an easier time working the problem on the bench,
ALSO you must check that the return spring can be compressed fully with some room to spare.
OR the spring will fracture and then small pieces of spring steel will cut your new seals to shreds,
solution remove as many winds as needed to allow the spring to compress with a bit to go before full compression, this could be cutting off a one or two winds
I don't remember the rebuild kit coming with a bunch of new hard parts so now I am worried. Seems like I reused all the springs and such and only replaced seals.
If you have a '79, and the ball stud for the release arm was not updated ..... there is an excellent chance that it is broken: it may appear to be in place, but if the teflon ball cup in the release arm has degraded, the release arm works against the ball stud and it snaps - it has no place to go, so may still appear attached.
Take the air cleaner assembly off, and put a pry bar into that ~20x40mm rectangle on the top of the upper bell housing .... and gently try to push the release lever back. If all is OK, nothing will move, and the full ~25mm diameter rim of the ball cup will be visible: if not ..... there is an update for the ball stud with a M10 vs the early M8 thread - that is prone to failure!
All that is required is to drop the exhaust, lower bell housing, clutch, and then slide the transmission & torque tube back to remove the upper bellhousing. one then drills & taps the latter for the update - piece of cake.
Short version - read this thread, and have seen this issue previously: easy to confirm yea or nay. Show us a good pic of the top opening, or do the test above> if broken, easy to talk you through any detail required.
Take the air cleaner assembly off, and put a pry bar into that ~20x40mm rectangle on the top of the upper bell housing .... and gently try to push the release lever back. If all is OK, nothing will move, and the full ~25mm diameter rim of the ball cup will be visible: if not ..... there is an update for the ball stud with a M10 vs the early M8 thread - that is prone to failure!
All that is required is to drop the exhaust, lower bell housing, clutch, and then slide the transmission & torque tube back to remove the upper bellhousing. one then drills & taps the latter for the update - piece of cake.
Short version - read this thread, and have seen this issue previously: easy to confirm yea or nay. Show us a good pic of the top opening, or do the test above> if broken, easy to talk you through any detail required.
Thanks All.
09-27-2010, 10:43 AM
#15
Rennlist Member
As some others have already suggested ... sounds like either ball stud/cup issue or intermediate plate adjustment problem. Symptoms you describe are classic for those two things. I had a combination of both on mine (worn out ball cup and maladjusted intermediate plate) and it just would not totally disengage when stationary .... stuck in gear, wouldn't go in or would go in but grind. There are a few threads on intermediate plate adjustment and modification which you'll find valuable. If both these things aren't right it can be a dog of a clutch.