P6 Clutch Master Question

Vern Klukas

Active Member
HI All

This is a problem with a 69 TC that I'm working on. New clutch, new slave cylinder, master cylinder condition unknown. There was considerable confusion over the proper clutch cover, but that has been sorted correctly.

Using either Harvey's method or the factory method for adjusting the pedal & throw we get: clutch does disengage, I'm able to get the slave cylinder to hit the lock ring and then adjust the pedal. The problem is, the clutch takes up very abruptly at the very bottom of the throw. The master pushrod isn't wet, and there is no puddle on the carpet although that can be deceiving. In any event, fluid isn't disappearing. The pedal doesn't feel particularly odd on the way down, maybe a little lighter than what I'd expect. I can't pump the pedal up appreciably.

To my mind, the master cylinder must be faulty so I'm about to rebuilt it. But it behooves me to ask "what else could it be?" before I do that. Any thoughts?

Yours
Vern
 
Vern, pressuming that the clutch cover is correct for the release sleeve, my first thought was that the master cylinder being on its last leg, the fluid getting past the front seal, so it can't move the proper amount of fluid to operate the clutch with the desired feel. It is just possible to disengage.
You say that the piston on the slave hits the circlip, but this doesn't mean that the actual travel of the slave is correct, if it is shorter than normal, it could give the feel on the pedal that you describe.
So i would start with rebuilding the master. In any case it is the easier thing to do before going deeper.
 
Are there any air bubbles visible in the pipe? I had real difficulties bleeding mine until I realised that the pipe was letting in some air. It wasn't leaking fluid out so I'd been fooled into thinking it was OK. A replacement pipe had it cured... for a couple of months, but now the master cylinder has started to leak so I've bought a replacement from Mark Gray. I had resealed the original master cylinder hoping that the minor pitting in the bore would be within tolerances. It only lasted a few months. And the 3 other master cylinders I'd stripped down were even worse.
 
Just a short update. Pulled the master yesterday, and it was indeed leaking. Not quite enough to run down the pushrod and get the inside of the car wet, but enough to (I hope) to give the symptoms observed. Now to kit it and reassemble. Fingers crossed.

Yours
Vern
 
Another update.

The master cylinder rebuild didn't change anything, so I decided to check the new slave cylinder that had been supplied & fitted (before I started on the car). And voilá, it has a 1" bore rather than the proper 7/8". So problem solved once I get a proper slave cylinder.

Yours
Vern
 
Erm, 2200s came with the 1" slave cylinder as standard, and as far as i know the master remained the same. At least this is what i am using in my TC, the standard master with the 1" slave, as this makes the pedal significantly softer.
Of course you lose nothing by trying the ⅞ one as it is the same with all A series transverse engined cars.
 
Demetris said:
Erm, 2200s came with the 1" slave cylinder as standard, and as far as i know the master remained the same. At least this is what i am using in my TC, the standard master with the 1" slave, as this makes the pedal significantly softer.
Of course you lose nothing by trying the ⅞ one as it is the same with all A series transverse engined cars.

Interesting. Looking in the parts book, the lever attached to the clutch shaft is a different part number, as is the clutch cover & disk, 2000 to 2200. I suspect that the 2200 lever will be 23% longer than the 2000 lever, that being the % increase in area, 7/8 to 1 inch bore. Also possible the 2200 clutch cover has less throw that the 2000.

It does match the symptoms: pedal is very soft, nearly full pedal travel is needed to disengage the clutch and the pedal travel between disengaged and fully engaged is much smaller than it should be.

We'll know soon.

Yours
Vern
 
This sounds like a bleed problem. Sorry if you have already gone down this route and it has failed but to get the air out of the slave, you need to push the piston in as far as you can into the cylinder, the while holding in place slightly release the bleed screw with a finger over the end so that the pressure does the job of evacuating the cylinder, but don't let all the pressure go. Then while holing everything tight, get someone to slowly press the pedal down and then hold it down, while you again evacuate through the bleed screw as before. Do that four or five times and you'll get all the air out but don't left the small reservoir run out of fluid.
I did just this process last night on a P6 that the slave had failed on and I was called out to replace and sort.

The pushrod will have a small amount of adjustment available on the threaded end, but if that isn't enough, you might want to consider taking the lever off the spline and moving it around by a few splines also.
 
Slight twist on Mark's approach (which I find infinitely easier) is to remove the slave from the bell housing and hold it about the level of the master. Use the push rod to push the cylinder all the way home and get somebody to press the pedal. You don't even need a bleed pipe that way as everything is 'uphill'. Same difference tho.
 
Slight twist on that... just turning the slave cylinder so that the bleed nipple is uppermost (rather than lifting it up and risking damage to the pipe) works for me.
 
Willy Eckerslyke said:
Slight twist on that... just turning the slave cylinder so that the bleed nipple is uppermost (rather than lifting it up and risking damage to the pipe) works for me.
Even better! Although I have a new plastic flexi pipe on mine so no issues there, but good point all the same.
 
Some closure on this thread. The majority of the problem was in fact the worn master. The 1" slave does affect the throw, but now that I've got the air out the bite point is acceptably high so case closed.

Yours
Vern
 
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