How much does rust impact a vehicle's overall function and safety?

Dear Car Talk

Dear Car Talk | Jan 01, 1999

Dear Tom and Ray:

How does excessive rust affect the suspension, braking, fuel lines and general
safety of a vehicle? How does rust affect the resale value of a car? Should the
owner of a car with excessive rust in the above systems be concerned? -- Bob

RAY: Yes, one should, Bob.

TOM: The things you mention -- suspension, braking, and fuel lines -- are
affected by rust. But the biggest threat rust poses is to the structural
integrity of the car. By the way, it also wreaks havoc on the resale value.
Exhibit A is the '79 Fiat Spider I just bought for 25 bucks.

RAY: And he overpaid for it. Most people think of rust as a cosmetic problem.
But when rust gets into the structure (i.e. the frame) of a car, it becomes a
serious safety problem.

TOM: You may never know your frame is rusted until you have an accident. Then
you're in real deep doo-doo. You thought you had a few thousand pounds of steel
around you for protection, and in reality, all you had was about 10 pounds of
ferric oxide dust, which disintegrates on impact.

RAY: And even before things get that bad, brake lines can rust out and leak, gas
lines can rust, shock towers and frame rails can rust out. All of these make a
car unsafe to drive for a variety of reasons. So you want to keep a close eye on
your older car and make sure you replace any parts that show dangerous levels of
rust. And when the frame is rusted -- that's when it's time to give the car its
last rites and send it to the crusher.

TOM: Or sell it to me. I like to sit in old parked cars in my driveway and go
"vroom, vroom!"

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