My wife's 2002 Outback's (LL Bean) brakes sometimes don't work when car is first started, either first thing in the morning when leaving for work or, less frequently, in the afternoon after a cold soak on the parking lot. Symptom is like the power assist has failed (no vacuum boost?). Car can be stopped by really standing on the brake pedal. Problem only shows up when outside temperature is below approx. 25 deg F. After 1 or 2 minutes of either idling or slow driving, problem clears up and car is fine for rest of drive. Any thoughts?

I have the same problem with my 1989 Toyota Camry. My mechanic says that water has gotton into some of the parts and freeze them when not being used. All you have to do it try to stop the car a few times before getting onto the road. That solves my problem.

I have the same problem on my 98 Legacy wagon. I'm pretty much an automotive idiot but my wild guess is that the serpentine belt (which is squeeking on mine) runs a compressor for the power assist. When the vehicle's cold, the belt slips badly. Power steering is also affected. I'm going to read up on it tomorrow & have ordered some belt lube. I'll post what I find. Please let me know if you figure the problem out.

Thanks for the feedback. I don't think it's the serpentine belt in my case 'cause the belt seems solid (that is, it's not squealing when cold) and the power steering is still OK. Hard to believe it's something (like water) frozen in one of the lines or someplace else that melts 'cause the brakes start working inside of a minute or 2 - not long enough for things to warm up much after an overnight soak at 20 deg F.

When the problem appears, I can sometime "correct it" immediately by really standing on the brakes. I'll feel something let loose and the brake pedal will push down maybe half and inch or so, just like someone had opened the bleed screw on the caliper (only the pedal doesn't go all the way to floor like when bledding brakes). After that, everything is fine.

Maybe I'll try flushing the brake fluid when the weather warms up a bit, see if that helps.