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jdfish

Clutch Pedal Pressure

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Whe cold my clutch pedal pressure seems as stock, but when out for a ride the pressure stiffens up. Some history; After messing about with master and slave cylinder rebuild kits that didn't work too well I have installed rebuilt units from SJS. I made my own pressure bleeder and have successfully bled the line (changed to braided stainless some time ago) Everything works fine except when up to operating temp the pedal pressure gets noticeably stiffer. I have roted the clutch line outside of the rear chassis section to stay away from heat/interferences. Is this simply the fluid heating up and expanding or is there something else going on?

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More likely to be something mechanical in the rest of the linkage; maybe the lever from the slave cylinder through the bell housing is getting a stiff bearing when it gets hot? Or the clutch lever itself on it's bearing, possibly. It's the force on the pedal that is increasing; with newly rebuilt master and slave cylinders and shiny new Goodridge hose, I doubt that the problem is hydraulic. Close inspection of the linkages ought to show what's wrong....have fun(!)

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Thanks for the guidance.

 

The lever into the bell housing moves freely when cold but I hadn't thought of a possible bearing issue on its pivot point 

 

Sounds like a winter project as long as things hold up over the summer. I imagine that a complete bearing failure could render the clutch useless.

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I can't see there being much chance of a complete bearing failure there, especially if it moves freely when cold. I think I'd try to isolate where the stiffness is...when the car is hot and the pedal is stiff, disconnect the slave cylinder from the operating rod and see what the pedal feels like. Don't go mad and push too hard, or you'll strain the circlip that retains the piston...just enough to see if the pedal is stiff or free. Push it back in again and have another go until you are certain. If it's stiff, then the fault is in the hydraulics or the clutch pedal assembly...if it's free, it's in the clutch linkage or the clutch itself. It could be the clutch pressure plate giving up, I suppose. Once you have isolated which end of the system is at fault, find out what's causing the problem....disconnect bits and see if it makes any difference until you find what does! I am beginning to think it might be the pressure plate....but let's hope not....  

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Thanks John,

 

Appreciate the advice. I will remove the slave rod and see if this isolates the issue.

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Crank shaft end float makes the clutch pedal move slightly, not sure it makes it stiffer though. You'll notice the clutch pedal lift up as you put your foot down on the throttle.

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Oh, Bibs, I do hope it doesn't!! Crankshaft end float ought to be 3 to 8 thou, maximum wear limit is 12 thou., so any end float on the crankshaft isn't going to produce any movement in the clutch pedal.....at least, I can't see any way that it can!!

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On my NA, the flywheel was moving so much the travel was going through the clutch to the selector fork and moving the slave cylinder which pivoted on it's mount, I felt it at the pedal! 

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You shouldn't have though!

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AAAAAAAAARRRRRGGGGGGGHHHHHHHHH!!!!!!!!!!

 

Other than that, me speechless........(!)

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Make sure the clutch lever free play (the arm coming out of the bellhousing) is correct (rotate the threaded bolt so it is not too lose or tight).

 

Then check the angle of the slave cylinder -- if it isn't pushing straight, or is at the wrong height, you can get the symptoms described.  Shim or grind the slave cylinder as necessary.

 

And as noted above, pray it is not the clutch pressure plate . . .

 

 

 - T

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.......well, lots of interesting thoughts....some rather frightening!!

 

I will look for pedal movement on throttle (maybe best done with a willing test passenger) but am sure that the slave is secure and bolted in tightly.

 

I've already checked the lever freeplay and the exposed threaded bolt is at spec.

 

I'm half suspecting some corrosion so may try to lube the pressure plate somehow..carefully

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Dont understand how it could be the pressure plate.  Pressing the clutch has no mechanical connection to the pressure plate whatsoever, other than lifting the cover away from it?   On a Citroen box, the release bearing is pressed onto a shaft that slides on a plain bearing, I suppose that could be dried out, or behaving iin some other odd way?

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Pressure plate is the one with the diaphragm spring, ending in little levery bits that the release bearing pushes on. If the diaphragm spring breaks, then you can get the whole thing jammed up solid and the clutch release mechanism won't move at all. Happened to me on a little FIAT....and before it did it, the pedal pressure went up, too! I think you've confused the pressure plate with the friction plate...

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just prey its not to much end float as I have as it can and has wrecked my block

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