On a nice drive last weekend, a new problem with my Series III clutch suddenly started. Sometimes, the clutch pedal operation is smooth and works normally. Gear change is smooth and without issue. Every once in a while, the clutch pedal feels like there is a mechanical binding that has it blocked and I am unable to push the pedal. Pedal return is always normal. It has never stayed like this for long and I have been able to release and then push through whatever feels like it is blocking the pedal. I crawled under the dash to examine the pedal connection and all looks fine but I was able to operate the pedal and could feel the resistance after a few strokes.
There are no leaks in either the master or slave cylinders and the hoses look OK from the outside. The fluid is a little dark in the reservoir however. I have not gotten the master cylinder apart to see if anything came apart inside but the ROM does not show an obvious failure mechanism that would lend itself to a periodic sticking of the pedal. My plan was to flush the system ans see if any crud, maybe from a deteriorating hose, comes out but my experience with bad hoses is they wont release, not block pedal depression. Any other ideas on what to look for here?
Someone recently, was it Mike Moore (?) had the clutch permanently freeze up. I don’t think we know the reason yet but most people think it’s hanging up on the shaft splines whether due to rust or debris. I’d look for external interference first. If that isn’t the case then exercise it to see if you can free it up.
Sounds like some kind of a hydraulic lock, that releases as time passes. If it was on a Ser I 4.2l car I’d suspect something going on with the valve at the end of the bore of the master cylinder. I’m not familiar with Ser III master cylinders, but suspect they have something similar.
One way to achieve this is that the master cylinder is not quite lined up correctly relative to the hole for the clevis pin at the pedal. The pedal moves in an arc but the piston has to move down the bore a straight line. It is possible that if not quite lined up right, that it’ll scrape along the master cylinder a bit. The symptom is that it appears to want to change gear best as though you double declutch it. If this is so, then the fix is to put a thin shim or washer under one of the bolts holding the clutch to the pedal box, but it may need a new master cylinder if it is already too scored to ever run run leak free smoothly again.
Clutch return is always trouble free. It takes a couple of thousand miles for this to manifest itself and I’d normally only suggest it for a car which has had an auto to manual swap as the oem setup ought to fit right first time, but a new repro clutch pedal could be a root cause if the gearbox is swapped. You’d also expect to lose fluid into the passenger compartment with this fault, but you don’t report that.
No there was no noise at all. I would loosen the bleed screw on the master cylinder and if the pedal goes down if it does out of it you can pretty much eliminate that part. I would then try to bleed the slave and see if you get fluid out of it. If so then you probably don’t have any crud in the lines.
I had a little foot surgery that kept me from tearing into the clutch hydraulics. I finally got it apart and found the fluid was the color of tar and practically no flow from the bleed nipple. Further tear-down took ~120psi to get the slave cylinder piston out with crud lining the sides and the bleed nipple plugged with rubber from somewhere in the system. I was apparently a good boy and Santa brought a new clutch hydraulic system that I have now installed.
I am now having an issue bleeding the system to get a firm, solid pedal. I first bled it without the return spring and got a solid pedal that felt good. I then added the return spring, my car was missing the spring, and cannot get a good pedal. It feels good after about half the pedal throw and I can see the slave move ~1 inch from below when I am bleeding it. I have tried all bleeding methods I know of: the ROM method of opening the nipple and slowly pumping, my normal technique of push, open then close and release, and just gravity through the open nipple. I still have a weak pedal for the first part of the pedal throw. I do not see any bubbles from the nipple and have run nearly a full can of fluid through it now. Good news is I do not have any evidence of the stricking issue that started this journey!
Hi Doug,
I was able to just gravity bleed the clutch on both my cars, the '68 and the '73. How much free play do you have, the manual say’s 1/8th inch for the S3.
Cheers,
LLynn
Lynn,
Thanks and now that I think about it more, I did not adjust the freeplay once I added the return spring. I can see not changing the length of the rod could cause my symptoms. I will look at that this afternoon.
Just curious, how long did you let the system drip when you gravity bled it? I get a steady drip when I open the bleed nipple now.
Morning Doug,
I stopped when I got a steady drip. One other thing I recall from my '68 which may or may not be relevant, the kit that came with an ‘extra’ dust seal and I installed it with both seals. It has been some time ago but having the extra dust seal prevented it from working correctly and IIRC it kept leaking, a long shot but thought I would share anyways.
Cheers,
LLynn
Thanks Lynn. I checked and had ~3/4 inch of freeplay. Adjusted it to the recommended 1/8 inch, built a pressure bleeder (turns out the lid from a 20 oz Coke bottle with a schrader valve fits the reservoir lid perfectly) and all is good now!
Now on to the completely rotten rear mount and speedo seal!
