New master cylinder, brake pedal on floor next morning??

Before I put the car away for the winter I noticed a very low brake pedal. Bled them and it help for a day or two then almost to the floor. Last weekend took a good look and saw fluid running down the firewall so I replaced the master with a reman unit. Bench bled it, bled all 4 wheels and had a nice solid firm pedal. Woke up the next day and noticed my brake lights were on and figured I hadn't adjusted the swith right. Nope.. got in and the pedal was all the way on the floor. Pumped it and got pressure but not as good as before, will check tonight and see it's on the again.
Any ideas??
Manual brakes. Factor front disc, rear drum. No leaks, calipers overhauled and lines replaced last year, rear shoes and wheel cylinders replaced year before. Rear shoes properly adjusted.