Car is a '85 tbird. Power Front disk/rear drum no ABS. Brakes have worked fine until yesterday morning. Suddenly the pedal needed to be pressed nearly to the floor to get any braking, and that was weak. I checked the fluid and the front (smaller) section of the master cylinder was low. I filled it up but its not helped. I don't think I've ever had to add fluid in the 9 yrs I've had this car except for when I bled the front calipers after replacing the hoses some years ago. I "think" that perhaps only the rear drums are working at present but am not sure.
Does this seem like a master cylinder problem or a leak elsewhere? Why did topping off the low section not help? Since it came on suddenly, I don't think it can be pads or shoe wear.
Thanks JH