When it rains and my truck sits over night the brakes lock up with the slightest touch of your foot when you first get in the truck.
Over the summer I had some vibration under braking at slow speeds so I serviced the front brakes, new pads/hardware and new rotors. When i was in there i found one of the guide pins was shot, the rubber boot had split and there was all sorts of nasty corrosion in there so I got a new pin cleaned everything up and the brakes worked great until recently.
There is no evidence of caliper sticking (no evident fluid leaks, no pulling under braking, no excessive heat or dust on one side). The only symptom is that the brakes will lock completely after it rains. As soon as you get up to speed and put some heat into them they function normally again.
Anyone have any ideas?