Heat shields aren't completely useless

Dear Tom and Ray: One of the exhaust heat shields fell off my Honda Civic Hatchback (2001) a while ago. The dealer told me not to bother putting it back on or replacing it, because I don't need it anyway. (1) Why does Honda (or any manufacturer) install the dang things if all they do is rattle and fall off? (B) After the heat shield had been gone for nearly a year, my exhaust manifold cracked. Could the missing heat shield have hastened the failure of the manifold?

Holly

Tom: To answer your second question first, the heat shield had nothing to do with the cracked manifold. So forget about that.

Ray: Why do they put heat shields on cars? C'mon, Holly. There are lots of car parts that do nothing but rattle and fall off. Why pick on the heat shield? The heat-shield manufacturers have to eat, too!

Tom: The heat shields are actually metal guards that surround the various pieces of your exhaust system. They're there to shield other stuff from the excessive heat given off by the exhaust.

Ray: There are top and bottom shields. The bottom shields are there so that if you park on tall, dry grass or some other combustible material, your 600-degree exhaust system won't set stuff under the car on fire. It doesn't happen often, but it can. And when it does, it's very exciting!

Tom: On top, the heat shield prevents the heat of the exhaust from going upward, toward the floor of your car. And depending on which piece of the heat shield is missing, that could cause the bushings in your shifter to dry out, or the bottom of your sneakers to melt and become one with the carpet.

Ray: The heat shield is made up of a bunch of cheap, thin pieces of sheet metal that are welded in place. And since they're all under the car and constantly exposed to the elements, they're particularly vulnerable to rusting and breaking loose.

Tom: Our lawyers tell us that we must always replace rattling or missing pieces of the heat shield. Why? Because they say they're already too busy defending us against libel lawsuits from the carmakers, and they don't have time to defend us on the off chance that some guy's dead day lilies, and the rest of his neighborhood, go up in flames. Not to mention his car.

Ray: But we know there are lots of people who choose not to replace heat shields. It can cost 20 bucks to just tear it off, versus maybe $200 to install a new one -- if you can even buy the piece you need individually.

Tom: And your dealer might know that -- based on the area in which you live, the kind of driving you do or your preference for asbestos-toed shoes -- your car might be fine without one particular piece of the heat shield.

If you're not permanently melted to the floor of the car, write back in a few years and let us know if he was right, will ya?