Brake problem.

[Whanson]

Ok so I have been having some brake issues with my car. Only the front brakes have been grabbing. I have tried bleeding and bleeding some more. I have replaced the brake master cylinder, proportioning valve, pads, rotors, drivers side rear caliper, upgraded to SS brake lines and DOT 4 fluid. I replaced the rear caliper bc it was not engaging at all but the parking brake was. Now on my passenger side rear the parking brake is not engaging but the caliper was. Now both rear caliper are not!
Yes I have adjusted the screw in the back to where it engages and then backed off a quarter turn. Any ideas would be greatly appreciated.

[Whanson]

Oh and when I press the brake down it will go almost to the floor and then it will start engaging the front brakes, and makes this "dry pump" sound if you will, until it gets to the "engagement" point.

[wakabama]

might be the booster

[Whanson]

Replaced the booster last night and bleed the brakes and they're finally working. ^Thanks for the help and thank you Kurt for the part.