I had the same thing about a year ago. I heard many things were possibilities, including the brake fluid heating up because the brake line was too close to the exhaust/heat. What seemed to fix it, however, was when I adjusted the brake linkage between the pedal and the master cylinder, so there was more room between the linkage and the floor of the truck, when the brake pedal was released. I think there was a spec in the book. - scott
