Strange clutch issue

I have a strange problem with a XK140 OTS, (original fourspeed, no OD).
The clutch is a Borg & Beck, I installed it all new two years ago and was working perfect until now.

There was some noise from the clutch when the clutch pedal was pressed down and the clutch was not released until the pedal was close to the floor and the car was hard to shift.

I adjusted the clutch links outside the belly house and the pedal feeling was now ok, But when I started the engine, it now was impossible to shift into any gear at all.
I tried to turn the engine over with just the starter motor, now everything seemed to work ok, I was able to shift and the clutch released ok.
I started the engine again, it was still impossible to shift and the clutch did not release.

I suspected a half broken tapered pin or a crack in the clutch fork, so I removed the gearbox, but found these ok.
I removed the whole clutch, still looked like new.

Then i measured the clutch plate as in the photo, with a ruler over the plate and against the six bolt holes in the clutch cover.
At four holes i got 3.3 - 3.7 mm, (0,13 -0.15) but in one direction it was 3,15 mm (0.125) on the bolt hole at one side and 4,2 mm (0.165) at the opposite side, Could this be the reason why the clutch dont release when engine running? Or do you have any other ideas?

Hope i made myself understood.

Thanks in advance
George

Plenty of grease in your crankshaft pilot bushing?
No rust between clutch disk and flywheel or pressure plate?
Slave cylinder bracket flexing too much?
Has clutch effort stayed the same or feel soft?

I’d replace the pressure plate.

Broken or sheared taper pin is usually the prime suspect, but you say you checked that as ok.
How is the carbon release bearing?
You might check the parallelism of the pressure plate center ring with the outer bolt pattern.
See if there is about equal effort to compress the 3 arms or levers.
Put the clutch disc on the trans shaft, turn it and see if there is much runout, non-parallelism.

Thanks for the input.
(The release bearing is almost new also.)
As you say, and I cant find anything else, I suspect the pressure plate.
I have adjusted the three arms for parallelism and the clutch disc is now sticking out 3,6mm at all 6 bolt holes where I measured in the photo.

I guess I have to get the gearbox back in the car to test if this was the problem, puh…
I will report back next week.

The car is now up running again and the clutch feels perfect. The reason must have been one of the three arms that holds the pressure plate. These arms are adjusted from factory and the nuts then locked. I guess one of the lock nuts failed to do its work.

Looking at the pressure plate, one can see its a little burned at one side.

A small adjustment for mankind, but a hell of a job for a man…

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I wish for you… to never have to do that miserable job, again!!!