Very odd brake problem

[Ex-User (107751)]

The fault started immediately after replacing the brake servo, a bit hard to explain.
Basically when I brake normally everything seems ok. All the normal procedures to test the servo and the master cylinder seem ok.
But if I fully depress the pedal I can feel and hear something "clicking", and the pedal loses resistance, so if I do it while driving I'm getting full brake power (emergency braking) without any effort. The moment I lift off the brakes completely , I can hear another "click", then the pedal resistance is back to normal.
I can play with the pedal from slight press to full without any effort, once I reach this "click" at the end of the travel.
I couldn't find anyone with the same problem on the internet. The mechanic says it could only be the master cylinder. Maybe the bleeding procedure damaged it (pressing the pedal too deep while bleeding).
The servo was removed and sent to inspection, then the system was bled again, no improvement.
Anything to check before changing the master cylinder?

 

[da rok]

if you unplug the vacuum hose do you still get full breaking power, ive had a case where the diaphragm was damaged which some how gave the car on or off breaks... but since you say the servo has been checked and there is clicking id re build the master cylinder, may have dislodged a o-ring or something

abs working?

 

[JB21]

Master or ABS pump.

 

[Ex-User (107751)]

Abs is functioning ok,
Can it really be the abs if it happens even while not moving and disconnecting the abs fuse?

 

[JB21]

Abs is functioning ok,
Can it really be the abs if it happens even while not moving and disconnecting the abs fuse?

The reason I say abs pump is the clicking noise, the pumps click when opening and closing the ports/solenoids. More than likely the master though mate. I have one in good working order with res attached if you want it, make me a reasonable offer if you need it.

 

[Ex-User (107751)]

I'm not from Europe ...
The clicking is clearly coming from the pedal , which seems more servo related than master cylinder ?
The servo was re-built, maybe it has a too long rod which presses too deep, thus the clicking? Wouldn't that cause the brakes to not release completely?