The brake pedal on my truck goes to the floor with firm continuing pressure. It still has brakes when it goes down; if you hit the brakes normally the pedal is fine but if you have to stay on them hard the pedal starts to go to the floor. Just left dealer with replacement of hydr-booster and master cylinder to the tune of $1225.00 and still doing the exact same thing as before I took it in. The mechanic indicated that he check all pads rotors shoes & drums and all are in specs; no leaks detected in the system. He performed automated bleed procedure on system as well. Any ideas? Thanks for any suggestions.