I have a completely stock 53 Chevy half ton than I have been using occasionally for the last 20 years, before which I completely rebuilt the entire brake system with new parts. I have had no problem with the brakes until I drove it on a rather long trip to a swap meet ; about 60 miles round trip. As i reached home on the return trip , I noticed I had virtually no free travel on the brake pedal. The brakes still engaged and stopped the truck without pulling to one side or another. The brakes now engage on contact with the pedal and I feel they might be staying partially engaged during driving. There is no mushiness and engagement is very firm. It feels like the system pumped itself up during the drive without my doing and stayed pumped up. I suspect a faulty master cylinder but hope someone on this site can advise me before I throw money at it. Thanks George