Is driving with a "holey" muffler dangerous?

Dear Car Talk

Dear Car Talk | Apr 01, 2003

Dear Tom and Ray:

I've got a '92 Honda Civic that has had a "hole in the muffler" sound for about a month, and my husband says it's fine to drive it that way. We need this car to go on a family visit (about 1,100 miles round trip), and it's our only vehicle that holds car seats for my 3-year-old boys. Are there any long-term hazards (to the car or to our health) to driving with a "holey" muffler? Personally, I suspect that my husband just doesn't want to spend the money, because it took two summers of driving around in central Virginia heat and humidity before I threatened to wreck the car and buy a new one if he didn't get the air conditioner fixed. (Mind you, I was pregnant with twins the second summer, and they were born in early July. He waited until late summer to deal with the A/C problem!) -- Diane

RAY: Oh boy, Diane. Your husband is obviously one of my brother's soul mates. I feel your pain. And I know my sister-in-law does, too.

TOM: Actually, this IS dangerous, Diane. To you, your family and the car.

RAY: Let's start with the car. Any hole in the exhaust system reduces the back pressure in the cylinders. The closer to the front of the car the hole is, the more the back pressure is reduced. And without sufficient back pressure, the exhaust passes by the valves faster, which makes the valves run hot. If they run hot enough, they can melt. And that'll cost your husband a cool $1,000.

TOM: While the valves are unlikely to burn out while you're driving around town, it certainly can happen on, say, an 1,100-mile trip. So tell your hubby to add to that $1,000 the towing fee, the hotel and the dozens of roses it'll take to even begin to make it up to you.

RAY: But more importantly, any exhaust leak near the front of the car can allow exhaust gasses to get into the ventilation system. And that can kill you. Even if the leak isn't up front, if you're driving an old heap -- like a '92 Civic -- and the heap has some rust holes in the floor because its cheapskate owner didn't take care of it, exhaust could get into the passenger compartment that way. So, either way, it can be very dangerous.

TOM: If your hubby doesn't think that "imminent death of his wife and children" is a sufficient reason to get the car fixed, Diane, then you have to push it into a lake and say "Oops." Or do whatever it takes to get him to give you the money to fix it. Then use it to engage a divorce lawyer. Good luck, kiddo.

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