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What we normally recommend for root canals and crowns:

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Dear Tom and Ray:


I own a 1984 Pontiac Sunbird with lots of extras. It's a super car for me, with one exception. Sometimes (not always) there is a very loud scraping sound when I turn on the ignition key. I try again and again, and finally, it will start normally. Despite this jarring noise, it has never failed to start. The mechanics who checked this out at my request have found no cause or solution. One even suggested it might just be "the nature of the beast." But in the back of my mind lurks the worry that it may be a major problem someday. Any suggestions?
Elizabeth

TOM: Well, Elizabeth, unfortunately, you're right. It will be a major problem someday--today, in fact. It sounds like you have a chipped tooth on your flywheel.

RAY: For which we generally recommend root canals and crowns.

TOM: Actually, the flywheel is a big gear that's attached to the engine. When you start the car, a little gear pops out of the starter, and meshes with that big flywheel gear. When it turns the flywheel, that gets the engine going.

RAY: If one or more teeth on the flywheel is broken, every once in a while, the little gear will mesh with that bad spot, and make that horrible noise.

TOM: The reason you can finally get the car started is that eventually, the flywheel turns a little bit, just enough to give the the little starter gear has some real teeth to grab onto.

RAY: But eventually, just like in your mouth, the area of bad teeth will get worse. And sooner or later, you'll get stranded.

TOM: So your best bet is to have a new flywheel put in now. And in the future, try not to start the car when it's already running (because that's probably how you chipped this flywheel in the first place).
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