Why are my new mufflers LOUDER than the old one?

Dear Car Talk

Dear Car Talk | Jun 01, 2000

Dear Tom and Ray:

For the past month, I have been trying to get a certain muffler company to put a
quiet muffler on my car. I originally brought the car into the shop because of an
incessant rattle. I was informed that the problem was a hole in the original
muffler. After the mechanic replaced the muffler, I drove the car home. But it
was so loud, I brought it back to the shop the next morning. He told me not to
worry. He said the new muffler has to "carbon up" before it can be quiet. I asked
him to come for a ride. He did and agreed that it sounded like a "motorboat,"
much too noisy for a 1993 Jeep Grand Cherokee. So he put in another muffler, and
guess what? It's louder than the last one! He again told me that the muffler
needs to "carbon up," and he asked me to drive it for a month and then come back.
Time's up. The muffler's loud, and I'm not happy. What do you say? -- Len

TOM: I've got to make a note of that one. ... "Muffler has to 'carbon up' to get
quiet." I'm going to try that on MY customers! That's very inventive!

RAY: He was hoping that in that span of one month, one of several things would
happen: A. You'd get used to the noise; B.You'd experience significant hearing
loss and cease to be bothered by it; or C. You'd be abducted by space aliens. Or
maybe all three. But he lost, so it's time for him to fix this for you.

TOM: There are two possibilities. One is that, when changing the muffler, he
accidentally created a hole somewhere else in the exhaust system. That's easy to
test. All he has to do is plug up the end of the tailpipe with a rag. If there's
no exhaust leak, the car will stall within seconds. If there is a leak, the car
will keep running and get louder, helping him pinpoint the leak.

RAY: But the more likely possibility is that the aftermarket mufflers he uses
don't have the same baffling as the original factory mufflers. We often have this
problem with Jeeps in particular. And the remedy, in this case, is to buy a
factory muffler from the Jeep dealer.

TOM: This guy can put it in for you. You can even bring him the part. But he
should give you your money back for the first muffler and put an original Jeep
muffler in the car. The part itself will cost you a little more, but tell him it
comes "pre-carboned," so there's no waiting. Good luck, Len.

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