Mercedes Benz 1986 420 sel brakes have no power, the pedal goes to the floor car doesn't stop!?

My 420 sel is having a problem. the car wont stop, the brakes wont work. However the brakes are fine and the brake fluid is full. I was thinking it could be the master cylinder but i just wanted to make sure. I wasn't sure if there's a fuse for the srs brake system, but when i start the car the srs light goes on then after a few minutes shuts off. When i brake i dont feel any pumping, the pedal just hits the ground. Previous to this the pedal would go down half way before stopping somtimes and sometimes would be fine. But now it never works. And theres no air in the lines because i tired bleeding the air out!