Don't have much experience with brakes, changed pads a few times on a couple ford pickups is all. The wife came home and said the brake pedal all the sudden is going almost to the floor before it starts stopping on her 02 trailblazer. First I checked the brake fluid then went for a ride. The pedal isn't goin all the way down to the floor board but maybe half way before it starts stopping. Any idea what may be causing this?