Our cars are parked outside, and this has just happened to our R Megane. It used to happen to our VAuxhall Cavalier as well. The VX garage saw the car on many ocaisions and swore that there was nothing wrong with it. WE changed most componenents and still no cure so we swapped the car. THe REnault has jammed after being parked for 2 days in very wet conditions, and I think that the problem has to do with brake linings swelling in the wet. By the time the car gets to the garage they have warmed up and dried out. The problem comes when you head straight out onto the motorway after having been parked for a couple of days. The linings heat up too quickly and boil the brake fluid, which can be quite alarming in heavy traffic. If you stop for half an hour and let the brakes cool down they work perfectly normally for weeks, until you leave the car parked in the damp again. (You have to spend a weekend with the relatives sometime)
The first time I noticed this phenomenon was after having the first asbestos free linings put on the Vauxhall. SO I blame the linings. When they are really stuck a good belt with a hammer (around the drum) usually helps things so you can get the car to a proper mechanic who will tell you there is nothing wrong for about £50. AND then you go round the same curcle again!
Huw Jones
January 2008