Hy there Guys my wife has a 04 trailblazer and the brake pedal goes right to the floor if you press hard enough
Her mechanic told her it was the front brake pads we done so I bought new pads&rotors then went to put them on and the pads were at 75% so I did not change them order a new master cylinder installed and bled brakes still the same so installed pads and rotor better but pedal still goes to floor brakes work but pedal feels soft
you can pump the brakes with ignition off and they feel very hard but as soon as you start the engine the pedal goes to the floor
was wondering if anybody has changed the (what I assume is the abs unit) after the master cylinder located on the frame rail below the firewall

 

Brake booster?

 

does it have a vacuum booster or hydroboost? any vehicle with hydroboost if you push the pedal hard enough it'll drop

 

how would you know if it has a vacuum booster or hydro booster