Well I got the car out after it sitting all winter and noticed the pedal went nearly to the floor. Popped cover on m/c and it was nearly empty. I have had a bad m/c on another bird here before and I could always hear the fluid gurgle back into the booster when it was bad. I refilled the master abit and I dont hear any noise when letting off the pedal. The master and booster are damp looking though and although I dont see any leaks I am convinced it is the m/c leaking into the booster. My question is what the effect of brake fluid might be on the booster if it seeped all winter, I dont know when it started this as all was well last fall so I will error on the side of caution and say it leaked all winter.

Anything is possible but I would recommend that you carefully inspect the entire brake system. If you had significant leakage into the booster, then it must be dealt with. The fluid is not necessarily damaging to the rubber parts but it is a dandy paint remover so, painted components are suseptable to corrosion from exposure to moisture/humidity. Look closely for signs of leakage at the wheels and the flex hoses too.

Yea, I know what it can do to paint, not pretty. Actually the hoses, wheel cylinders, and lines are all newer. I used to live in Fl and I drove this car alot, year round. Now it is lucky to go a few hundred miles a year. I have a parts car here that I bought in Fl that had a 30k restore done and then went out and had brake failure so just trying to be preventative in any way possible.