I rebuilt master cylinder and replaced entire rear wheel brake system. Have bleed system and have reasonable pedal. When you first get in truck and push brake pedal it will go to floor, but after one pump it is okay?? I did not bench blled master cylinder before putting back in truck. I have since bleed all wheel cylinders and got good flow, but still have pedal going to floor when you first hit pedal?? Any suggestions?? THANKS DAVE