Crusty's Exhaustive Brake Job

Dec 07, 2002

RAY: This puzzler took place some years ago, when Crusty the mechanic was in our employ and still was in possession of his faculties.

A schoolteacher had taken his car into us, and we had done a lot of brake work on it. He came in one day and said, "I'm kind of disappointed. Now that the academic year is over, I've been doing a lot more driving. During the school year, I drove back and forth to school, and everything seemed fine. Now I'm on summer vacation, and I've been taking a lot of long distance trips.

"I've noticed that if I'm driving on the highway for any period of time, when I get off the highway I often lose the brakes. I step on the brakes and they sink to the floor."

So, we put the car on the lift and we pulled off the wheels. We went over everything we had done to the car, checking to see if the calipers were free, the brake hoses free. Everything was fine.

Crusty, meanwhile, was just sitting there in the inky shadows not saying a thing. Finally, after we determined there was nothing wrong with the brakes, Crusty said, "When did you have the exhaust system replaced?"

The fellow says, "As a matter of fact I did have it replaced -- just before the end of the school year."

Crusty says, "That's the problem."

And that's the question.

How in the world could someone's exhaust system affect his brakes?


TOM: And how did Crusty know?

RAY: What Crusty knew was that we had eliminated everything else. And without even looking, he knew that the people who put the muffler in the exhaust system had done something awful. They had put the exhaust pipe touching one of the brake lines. Now exhaust temperatures can run upwards of 500 degrees. And brake fluid boils at something less than 300 degrees. This was a recipe --

TOM AND RAY: For disaster.

RAY: So when he drove the thing, it sustained high speed in the summer. The exhaust system got that brake line really hot and the brake fluid turned into a vapor and made the pedal sink to the floor. And, of course, by the time we got the thing, everything was cooled off and worked normally. But when it was hot, it would fail because the brake fluid had turned to vapor.

TOM: And, as we know, vapors are compressible and liquids ain't very.

RAY: Who's our winner?

TOM: The winner is Regina Warren from Suffern, New York.

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