I am currently in the process of rebuilding a wrecked truck. I have replaced all of the - brake lines - calipers - wheel cylinders, - pads, - shoes, - brake booster, - master cylinder

However when I start the engine the pedal still goes flat to the floor. I have bypassed the anti-lock system and still goes to the floor. I have bleed the system both manually and with an vacuum system, still having this problem used 3 boosters and 3 different master cylinders.

Am I doing something wrong? How can I fix this problem?

  • 1
    what is your make/model/year of vehicle? Is it all stock parts? What did you use to vacuum all the fluid out? Welcome to Stack Exchange. Cheers! Commented Mar 1, 2016 at 22:17
  • If it's a GM you probably have to actuate the bypass modulator valve.
    – Ben
    Commented Mar 1, 2016 at 22:18
  • If it's a modern car the pedals may have collapsed if it is wrecked, which could mean you have to replace the pedals
    – George
    Commented Mar 1, 2016 at 22:54
  • 1
    Did you bench bleed the master?
    – rpmerf
    Commented Mar 2, 2016 at 13:55
  • 1
    Possible duplicate of Brake pedal goes all the way to floor, after ABS was activated
    – George
    Commented Apr 5, 2016 at 11:36


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