I'm still pointing to calipers for several reasons.
First, did Goodyaer check the calipers while the brakes were dragging and smoking?
Second, cool weather causes the brakes to run cooler. Keep in mind that the brakes are right in the airstream that is passing by your car as you drive. Cooler air means better cooling for the brakes.
The condition I previously described is caused by aging of the brake components. Small bits of powdered material are released by normal operation of the brakes. In combination with some deterioration of the fluid, these fine particles build up around the seals in calipers and wheel cylinders as well as the moving parts in the master cylinder. Over time, and in combination with the expansion caused by heat from braking, the caliper can begin to bind. It doesn't take a lot to cause the brakes to drag slightly. This builds up even more heat, and it becomes a vicious cycle. Brake drag adds more than normal heat, causing more than normal expansion of the piston. Since the piston is made of a different material than the caliper body, it expands at a greater rate. This causes the caliper to bind even more, and the brakes to drag even more.
Once the brakes cool off, the piston will shrink back to its original size, and the caliper will appear to be acceptably free.
The problem must be diagnosed WHILE the problem is happening. Otherwise, there is no sure diagnosis. If there is no pressure in the line to the caliper, then that only leaves the caliper as the cause of the problem.
IF there is pressure in the line, that would point back to a problem farther back in the system. When you release the brakes, there should be no pressure in the lines. This would be an unusual condition.
Also, you did mention that the pedal had gone to the floor. This is caused by the fluid actually boiling in the brake system.
My feeling is still that your problem is the calipers.
Tuesday, December 30th, 2008 AT 11:15 AM