Join Date: Sep 2004
Location: Western Wisconsin
Car: '03 Outback H6-3.0 Black Granite Pearl, base model with cold weather package and cloth seats.
Feedback Score: 0 reviews
It is water in the vacuum line from the manifold to the brake booster, freezing in the check valve.
You can remove the hose when warm, and flush thru with some WD-40 and clean the water out of there. Then re-install the hose and you should be good for a while until you get significant water in there again. Pay attention to which end goes where....
On the really cold days, I always pump my brakes a few times before moving into Drive, to ensure that the valve is free. If it is sticking, and I get the rock hard pedal, a few more pumps is enough to free up the valve and return normal brake function. I learned the trick the hard way, almost rolling thru a busy intersection because I didn't check first. Some times you really have to stand on it, but you can free it up thru pumping the pedal.