Guy at the garage bled brakes. Brakes work fine now. duh. Truck sat for a couple months,then I put less than 5 miles on it. Brakes worked fine til last time when peddle went to the floor. Truck(a 40')has original ,rebuilt single master cylinder. Did air get into brakes while truck sat? Any ideas? Don't have a ton of confidence in those brakes.Lines etc are all new.Thanks.