bad master cylinder?

[spdracer@mail.utexas.edu]

So around a year and a half ago... I was bleeding the brakes and let the fluid
run low.  Opps, got air in the master cylinder.  So I finally bled the master
cylinder yesterday and the firm pedal was back; it would get firm after
pumping a few times.  Now today, it won't do it that anymore (and I just bled
the calipers again).  I can pump the brakes but they won't become rock solid,
there's still some movement.  I tried it on my mom's car and the pedal becomes
rock solid.  So.... it was fine yesterday but not anymore.  And while driving
today, I noticed the pedal getting softer.  When I was bleeding the MC
yesterday, it seemed like fluid was leaking out of one of the ports (without
any pedal movement) and that shouldn't happen right?  Otherwise, still stops
hard and I can lock them up at will, just have that bit of mushyness.  Also,
whenever I bleed the calipers (like 8 times the past year trying to get rid of
the mush), it seems that the RF always has air..... the others not so much.
Any ideas?

Khiem