This willl be obvious to most, but it took me a bit ot time to figure out, so it might be of use to some. I had excess free play in the brake pedal, yet adjustments were all fine, and the pedal didn't slowly go down when holding it, so it seemed the master cylinder was probably OK. But the master cylinder has two pistons -- one for the front brakes, one for the rear. Depressing the brake pedal applies pressure to the rear piston, which pushes fluid to the rear brakes, and also pushes fluid inside the cylinder to apply pressure to the front piston. If that fluid leaks back past the rear piston -- as was happening in my case -- the rear piston continues forward until physically hitting the front piston, finally applying the front brakes. That leads to excess pedal travel, and incidentally, to the rear brakes probably not being applied. So a new master cylinder fixed the problem, and now pedal travel is back to normal.
