I had to slam on my brakes a few days ago to miss some tourist who pulled out in front of me at like 50 and the ABS sure don't work anymore - but thats a different story. Well after this my brake pedal is really mushy when it comes to using it softly like in traffic. I have pretty new brake pads. They still have at least an 1/2 inch on them. The brake fluid looked pretty black like oil so I figured a good brake system flush would do the trick. I bought a one man bleeder thing at Advanced auto with a few bottles of 5.1 fluid. Did the whole system flush yesterday. Well today driving home from work in traffic the pedal went all the way to the floor when I press it very slowly, but if a hit it hard the brakes work like their supposed to. I figure its the Master Cylinder, but I wanted to get a few more opinions first. I also checked the vacuum check valve and it is working fine.

Anybody else have any ideas?