2002 Eldorado Collectors Edition Brakes..
 

My 02 Eldorado blew a metal rear brake line going over the rear axle last week. The fitting were rusted tite so I bought new line, the new GM proportioning valve that's in the line and the left rear brake hose and rear center hose. I then bled the brakes and tested and the pedal goes to the floor. I rebled the brakes and same thing. I then noticed that I ran the fluid reservoir out of fluid...dam it! So.. I then bled the rears again and went to the fronts. Bleeders were rusted tite. I got two new front brake calipers and put them, bled the front brakes..and still pedal goes to the floor. I then REBLED all the brakes again with no air coming out of any of the 4 bleeders. Still pedal goes to the floor?? I wanted to get some advice before I have to take it to a dealer as I know they are going to rape me. I was thinking of replacing the master cylinder but don't wanna start replacing stuff that isn't maybe bad? It hasn't tripped and codes either for the brakes..Any help is much appreciated!!

Anyone??????