383man has it correct. the piston in the master will stop when it "stacks up" against the piston with the leak. this will feel like it's to the floor, but is just the "stacked" piston hitting the end of the master bore. this can be observed when bleeding a dry system. you always start with the caliper/cylinder farthest from the master, usually the right rear, unless you have a cross system deal, or anti lock system that says otherwise. press down lightly and measure where the pedal ends up. bleed both rear brakes until there are no air bubbles using your favorite method. when satisfied, lightly push down and measure. it will seem and feel like you are on the floor, but in reality, you will be higher. the amount depends on the particular system, but higher it will be. bleed the front, and when done, you have the pedal you need, at the height you want. if the system were in fact connected, you would not lose your brakes, then look in the master and find one cavity full, while the other cavity is empty. i know it doesn't sound correct, especially when playing with today's masters that are different, in the fact most [if not all] have only a 3/4 wall dividing the two cavities, and a low fluid light warning when the fluid gets to a certain level, so as to not have a cavity go dry when coming to a stop or accelerating, washing the fluid over the dividing wall.