Cadillac Repair: New Master Cylinder?, air leaks, master cylinder

Question
I have an 83 Caddy Deville. One night I noticed the brake pedal was a little mushy. The next day, it went all the way to the floor and only slowed down the car when it was pumped against the floor. There is still plenty of fluid in the master cylinder, Do I need a new one? Or maybe just a bleed? Its snowing like crazy here and I dont have a garage so I want to be sure before I start.

Thanks!
Will

Answer
IF you are NOT losing any brake fluid from the master cylinder and you are NOT hearing any type of air leaks from under the dash when you step on the brake pedal This would most likely in 99% of all cases be a fault within the master cylinder PROVIDED you are NOT losing fluid from the master cylinder.