My grandmother had a bit of a scare yesterday. She doesn't drive her Fiat Punto (8 years old, 12k km or so, bought new) very much (it is, in effect, the Real Thing of the 'always driven by an elderly lady' car -- maintained at a local garage on a yearly basis), but yesterday she went to take it around a block or two, mainly to keep the battery from running down (again), and as she described it, the brakes started working less than stellar, and eventually failed completely -- no resistance to the pedal.
She got it home, carefully and with the handbrake. When I looked at it this afternoon, all the fluid levels including the brakes appeared to be in good shape, and starting it up revealed no immediate warning lights[1]. With the handbrake released, I could move the car back and forth by hand easily, but with the brake pedal depressed (which does not now appear to go down to the stops) it had at least enough braking to stop me from doing that (this is not necessarily inconsistent with there not being enough braking action to matter when acting on a ton of metal moving at speeds, of course).
So, what the hell happened? My pet theory: She left the handbrake on a notch or two and the drag caused the brakes to heat up enough to boil the brake liquid. If the garage doesn't find anything wrong with the brakes in the area of things that are actually broken, this'd be my best theory. Are there any other options that cause the brakes to fade out to nothing gradually (that tends to argue against, say, a piece of the caliper breaking off), and possibly return after cooldown?
Jasper
[1] I don't have a license, plus I don't like brakeless cars, so I didn't drive it.