Hydraulic systems are supposed to be closed systems, so the MUST either be a leak that's allowing air to enter when the pedal is released, or there is a component that is unable to hold the pressure generated by the pedal - either through volumetric expansion (e.g. a weak hose), or through leakage (e.g. a caliper piston, fitting, bleeder valve, ABS actuator, master cylinder). The only way I know to find such a thing is to trace it down methodically.I still haven't had time to look any further into the brake situation. What else would cause a soft pedal that goes almost to the floor?