[fred cook]

With a seized brake caliper, usually what happens is that the piston gets stuck in the bore because of corrosion. Remember, brake fluid is anhydrous (absorbs moisture). So, when the brake is applied, the piston presses against the brake pad and thus the rotor. However, because of the corrosion, when the brake pedal is released the piston does not retract keeping pressure on the pad. After being driven for a while, the pad will wear down releasing the rotor, but the next time the brake pedal is pressed the wear and excessive friction starts all over again. In severe cases, the heat generated can be enough to cause the brake fluid/water moisture mix to boil causing the brake pedal to go to the floor when pressed! Not much fun when you really need to slow down! Another thing that can cause a similar problem is that the flexible brake hose can deteriorate and cause the caliper to hold pressure. Either way, it's time for some brake work!