Brake Pedal's Odyssey to the Floor Unraveling the Enigma

The pedal seemingly randomly goes to the floor with little/no braking effort mostly at low speed or constant braking situations. The brake pedal falls to the floor without much resistance when the car is on. Is this a common problem with these cars? What could be the problem? If the brake pedal touches the floor, it typically means your brake master cylinder is going out. There is a hydraulic seal in the master cylinder that is ... A bad power brake booster could make the brake pedal go to the floor only when the engine is running, which is the primary issue that I am experiencing. After I start the engine though, the pedal has no pressure and goes to the floor. Yes, the new caliper is mounted correctly with the bleed screw on top. Some things I would check: 1. Is the fluid level dropping in the reservoir? Check for leaks throughout entire system. 2. Look at the fluid in the reservoir and ... Yes, the pedal should drop when the engine is started and vacuum is supplied to the booster, but the pedal should not go all the way to the floor! Pump up the pedal until as hard as it will go, hold the pressure, activate IN, it probably won't move but if it does, bonus! My brake pedal feels normal (resistance at about half travel), until I push harder than I usually do, then it feels like it's going over a hump and drops to ... After bleeding the pedal seems hard until I start the car and then the pedal goes slowly to the floor. Can't find any leaks and the fluid level in the ...