I’ve just had a problem come up with one of my XT disc brakes that I’ve had before on another bike and never got to the bottom of (even with LBS help).
The main issue is that the brake lever intermittently feels like it is “jammed on” giving no feel or modulation when braking. Normally, there’s a reasonable amount of pull before the brake starts to bite and then some more until it is full on.
When the brake plays up, there’s virtually no pull and the brake is full on.
From previous experience, bleeding the brake and even opening it up and giving it a damned good clean makes absolutely no difference as this problem.
While we couldn’t confirm it, the LBS thought that some grit or something might be lodged in the chamber in the brake lever that you just can’t get at, no matter how hard you try.
Has anyone else had a similar problem and, if so, what did you do to solve it?
On an another matter, I’m pretty sure the caliper has a lazy piston as well. It is really annoying!