I had master cylinder problems with mine after the drivetrain shop put the wrong fluid in after installing the tru trac in the front. Seals in the MC went bad and my dash light started flashing. Does your pedal feel spongy? If so this may be the case. After I replaced the MC and flushed the system, the brakes are perfect.
If there's a will, usually there's a way, but then you get to that bolt that you still can't get to with two extensions, two universal sockets, and a contorsionist midget trying to help you.
1999 XJ Four door, mostly stock for now, but I am in the process of building a custom plate bumper.