I have had a tech in the jeep while I'm underneath it.... pump, hold, crack the bleeder screw. it will build some pressure when it's not running... I have tested the brake booster and it tests good. The pedal goes to the floor when running. It is not a fade away it is just straight to the floor when running. I thought brake booster but if that were to fail then I would have a pedal rock hard, at least in my past experience...