@Tester One of the shops we took the car to mentioned that it might be ABS. I’ll find that fuse and pull it if/when the problem re-occurs. Thanks. I also liked your answer over in Sticking Front Brakes :
“Over time these hoses can deteriorate internally where a hunk of rubber delaminates and hangs inside the brake hose. This hunk of rubber can act as a check valve. That is, when you apply the brakes the pads clamp the rotors. But when you release the brakes, that hunk of rubber prevents the hydraulic pressure from releasing the caliper pistons. So the brakes remain applied.”
@It_s_Just_Me My wife did not recall which brakes were hot. She just mentioned that she could smell hot brakes. “sticking piston in the brake master cylinder”: sounds about right. Strange that it’s so intermittent. Hasn’t happened again since last Sunday.
@George_San_Jose1 “first thing I’d do is test if the brake booster is able to hold vacuum”: would this be likely to lead to intermittent/occasional failure sticking?
The part that still puzzles me: why does it unstick after a few minutes? It’s not the external temperature; this happened with the car cold/warm in cold/warm temperatures. It’s not at car-start; this has happened after driving the car for a few minutes.
Thanks for your help!