Dear Tom and Ray:

I have an '81 Chevette which I bought new in 1982. In January it wouldn't start, so I had it towed to a garage. It turned out to be a crankshaft bolt that had broken off. They removed the broken end and put in a new bolt. On the way home, the car started making a rattling noise, like something was loose. In three weeks, the bolt broke off again. I had it towed to the same garage and had to pay a second time. They put in a new bolt. It started the rattling noise again, and in four days, the bolt broke again. I can't keep paying for the same repair. They said Chevettes are notorious for this problem. Why won't the bolts hold? I'm 80 years old and don't look forward to taking busses all summer.
Paulene

RAY: The bolt you're talking about is the bolt that holds the crankshaft pulley onto the crankshaft, Paulene. And as far as I know, Chevettes are not particularly notorious for this. They're famous for falling apart in lots of other ways, but not in this way.

TOM: Something is causing the bolt to loosen up, and that's why it keeps breaking. It may be that they're not tightening it enough. But that's unlikely since they've had three tries, and have probably given it their best Vinnie Gumbazz twist.

RAY: It's possible that the pulley is warped. The pulley may be wobbling so badly that it's working the bolt loose. If that's the case, a new crankshaft pulley with your next new bolt ought to fix it.

TOM: The other thing to check is the threads inside the hole in the crankshaft. They could have been damaged when the bolt first broke, or when the mechanic tried to drill out the remains of the original bolt.

RAY: If that's the case, you have two choices, Paulene. You can either get a new crankshaft, which is what I'd recommend to most people in this situation. Or you can just have the bolt arc-welded to the crankshaft, which is inelegant, and entirely appropriate for a 1981 Chevette.