OK, thank you!! Good to know. I will check that out and do the WD-40 thing. Give me a couple/few weeks and I'll report back with results.
Regarding the bit about "should be good for a while until you get significant water in there again", is there something else wrong given that water gets in there AT ALL? Or does that just happen with the Outbacks? Is there anything I can do to prevent water from getting in there again?
Brake fluid absorbs water ie moisture over time it needs to get flushed to get rid of the contaminated fluid every so many miles pending your location conditions etc.
Its really simple. Iced check valve will not allow vacuum on the booster which equals hard pedal due to not having any assist from the booster. After the engine warms up, the heat generated by the engine melts the ice in the check valve and allows the engine to pull a vacuum on the booster easing the pedal effort.
Water in the brake system can cause high pressure on the brakes. Especially at negative F temps. With the heater running in the car, it would assist in thawing some of the lines. Its more likely a brake booster issue or a frozen check valve. If the car has a check valve. Some don't.
If there is a tear in the booster diaphram, it can pull in moisture.
I saw that you're also in VT, so it's at least good news that you still have the car. I was slightly worried you were going to reply with, "Nope, we sold the car this past summer in Montpelier, and it was white with 55k".
I drive through Montpelier every day. The intersection I spoke of is where rt 14 hits rt 2 in east Montpelier. Small world. BTW the brakes were fine today...