back brakes on 1996 chevy corsica

I don't know where the leak was coming from, so bear with me. First, if the pedal goes to the floor, either you still have a leak or the master cylender is bad. Also, when he repaired the leak, he should have bled the brakes. If he didn't do that, it needs done. If that still doesn't help. Recheck for leaks, check the rubber brake lines on the front to make sure they are not expanding when the brakes are used, and if all is good, my guess is the master cylender is bad. (NOTE: Tell him to make sure the rear brake shoes are properly adjusted. That can give you a low pedal, but it shouldn't go to the floor).