After winter storage, the brakes do not fully release, with all 4 wheels semi-locked. The car can be driven, but there is considerable additional friction. When I pump the pedal, it feels "dead". The master cylinder is a replacement, purchased new from Moss about 7 or 8 years ago. I use a silicone brake fluid. I suspect a problem with the master cylinder, since all 4 wheels seem to be equally affected. Anyone else ever have a similar experience? Any suggestions as to a possible root cause before I start taking things apart?