I was pulling into a handicapped parking space today at the grocery store and when I tried to stop my brake peddle went the whole way to the floor and the brakes wouldn't work. Thank God I wasn't going fast and the car in front of me was a Hummer! No damage done but could have been really dangerous as I just came off of the interstate doing 55 mph. Of course I had the car towed and was told it probably is a master cylinder. When waiting for the tow truck I would step on the brake and the pedal would go the whole way to the floor. After I pumped it several times it would tighten up. Does this sound like a master cylinder to you experts?