Left my 99 Disco I at home for three weeks over christmas break, came home and the brake pedal went straight to the floor when I got in to go to school. The back half of the brake reservoir was full, but the front half was empty. I filled it up, bled the brakes, and everything seemed fine. After a few weeks it seems like the pedal has gotten softer. I believe the master cylinder is bad, but I wanted to get some input before I coughed up nearly $200 to buy a new one.