ABS light and Parking brake light came on all of a sudden last night and brake fluid almost gone. I replaced a leaking wheel cylinder on the rear driver side about 3 months ago. I don't notice any leaks anywhere though and it went from everything fine to brake pedal going to the floor after it was sitting for about 7 hours. I've added brake fluid and the pedal still goes to the floor.

 

sounds like internal issue in the master.....might need to replace....