So I'm in Michigan here, and the last 2 days I've had no power brakes when I've gone to drive my kids to school. Brakes work fine without power, and I can drive safely with the extra effort, and thankfully the kids are with their mom so they're away until Monday... And things are supposed to warm up later this weekend or next week. It clears after some amount of run time.

I'm at 40,000 miles so it's out of warranty. Looking for ideas as to where the problem might be, and what repair I might be able to do. Fairly capable mechanically as an engineer. I could at least use a good diagram of the system, my guess is it's acting like there's water at some point in the vacuum system and it's freezing, and it must be somewhere that gets warmed up when the engine runs.

I'm pretty sure this isn't supposed to happen, as the power brake booster ought to work to -30 F

 

if there's water in the system, maybe a good long drive at operating temp will dry it out.