Is it safe to drive without a heat shield?

Dear Car Talk

Dear Car Talk | Feb 01, 1998

Dear Tom and Ray:

I have a '92 Honda Civic LX sedan which developed a vibrating noise a few
weeks ago. My mechanic said it was probably a loose heat shield, and I
figured he would tighten a clamp or something. So imagine my surprise when
I came back later to find he had removed the heat shield entirely. I asked
him if it was safe, and he said it's perfectly safe. I'm not convinced,
however. Why would the Honda engineers have put it there if it wasn't
necessary? -- Robert

RAY: Well, if you took your car to 1,000 different mechanics, Robert, 999
would probably do exactly what this guy did, and charge you $25.

TOM: And the other guy -- the one who'd been sued because a customer's car
caught fire -- would have installed a new heat shield and charged you over
100 bucks. And we'd have to endorse that guy's action, mostly because our
lawyers insist upon it.

RAY: Most cars have several heat shields ... .some more important than
others. The one most commonly removed by mechanics fits just below the
catalytic converter. It's designed to keep a hot converter from igniting
stuff underneath the car, like dead leaves and tall, dry grass you might
park on top of.

TOM: So if you live in a city, and never park in a dry meadow, you can
probably get by without that heat shield. But there are situations where
something is wrong with the engine and too much fuel pours into the
converter, causing it to overheat. And under those circumstances, the
converter gets red hot and can ignite something and set the car on fire if
no heat shield is present. And that's really why the engineers put it there.

RAY: Not that having your car catch fire is always a bad thing, Robert. My
brother's car doesn't even have a catalytic converter, but he installed one
hoping that he could get his car to spontaneously engulf itself!

Get the Car Talk Newsletter

Got a question about your car?

Ask Someone Who Owns One