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Failed brakes can be due to any of several causes

SHARE Failed brakes can be due to any of several causes

Question - My adult daughter was driving my 1988 Toyota Camry when she was involved in an accident due to reported failure of the brakes. She badly bruised the palm and little finger of her right hand in an attempt to apply the emergency brake. It was a hot and humid day. The Camry, with about 91,000 miles on it, has been well maintained. The Toyota dealership, to which the car was towed, could find no evidence of brake failure. Do you have any idea what happened? - Mary

RAY: I have a couple of ideas, Mary. One is that your daughter was driving with the parking brake on. Even if it was only applied partway, that could still be enough to heat up the brakes and cause a problem.TOM: When a brake is left on like that, the heat from the resulting friction can actually make the brake fluid boil. And boiling brakefluid can't make the car stop.

RAY: That would also explain why the dealership found nothing the next day. Once the parking brake was released and the brake fluid cooled off, there would be no evidence whatsoever. In fact, even an hour later there wouldn't be any evidence.

TOM: If your daughter is absolutely sure she didn't leave the parking brake partway on (if she's one of those people who has already made this bone-headed mistake once and now checks the lever twice before putting the car in gear), then there are a couple of other possibilities. One is that she's a "two-footed-driver," which could also explain overheated brakes. You can test that theory by driving behind her and seeing if the brake lights are constantly flickering on and off.

RAY: It's also possible that your daughter has nothing to do with it. A sticking brake caliper would have the same effect as leaving the parking brake on. The only reason I'm less inclined to believe that is that the dealership would probably find evidence of a sticky caliper after the fact.

TOM: Another possibility is a master cylinder failure. That could also fail intermittently (and, under rare circumstances, show no evidence later), but I'd lean toward the parking-brake theory.

RAY: And by the way, Mary, you probably have a pretty good idea now why carmakers - at their lawyers' suggestion - have changed the name from "emergency brake" to "parking brake."

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