I've had the same problem with my brakes. My two rear drums locked up when it got below 0, it tooks a ton of de-icer and a bunch of rocking back and forth to get em popped open.

I think moisture up in the drums froze them over pretty good, although I'm not sure why it would be that bad for you at around 30 degrees?

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2003 Edge 3.0 2WD Flex Fuel
Z liner | Truxendo bed extender | Mustang dome | More mods to come...