My rear brake went completely slack on me today, and not at the best of moments as was up on the eastern end of The Pentlands. Possibly coincided with the bike (and me) being blown over (I wasn't riding at the time).
Walked/slid down and sometime later as I cycled down the path from Straiton back to town it slowly returned, and seemed fine by Musselburgh.
I there anywhere that air can hang out, not effect the brakes normally, but get into the cylinders or pipes when the bike is inverted?