So i replaced the hydroboost on my 2001 ram and i cycled the steering both with the truck running and not running. Now my brake pedal goes to floor with zero resistance and will not return on its own at all. I did not undo any of the brake lines when i did the switch i don't think that i caused any air to get into the lines. What could be the problem? Could it be a bad hydroboost or a bad mastercylinder? Is there a way to test them? Please help. Thank you for the replys.

 

How about with the truck not running? If you can put the pedal down pretty easy with it off I'd imagine the master is no good. I do recall some time back someone had a similar experience and it was a bad hydroboost though. Good luck.

 

There is a diaphragm or something that you have to take from your old hydroboost unit and put in your new unit or the pedal will go to the floor. I had the same issue when I replaced mine. Just don't remember exactly what the part was.