Novel F Brake Problem

Having searched I didn't find another example, so…



Brakes were more alarming than spongy, changing the fluid didn't help, hoses pads, disks and callipers all good (and obsessively bled).



Symptoms:

Nothing seems to happen when first applying the pedal, although on further application it is possible to lock all 4 wheels. Servo appears to be working (pedal goes down on starting engine which pedal fully depressed), and pedal effort seems fine.



Cause:

1" of pedal free play before the plunger on the master cylinder starts to move. The return spring is all I'm pushing against in the meantime.



Working through the linkage I discover that the bush on the clevis pin at the master cylinder end is (mostly) missing.



Solution:

A new clevis pin. But, is this a known fault, and if so, why has the bush failed? Lack of lubrication, or is there meant to be a limit stop on the pedal assembly???

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