Turn the heat ON if a car is overheating...what?!?

Dear Car Talk

Dear Car Talk | Jan 01, 2001

Dear Tom and Ray:

I'm 15 years old and live in Texas. I recently finished driver's education,
and I could have sworn I heard my driver's ed teacher say that when your
car overheats, you should turn on the heater. My parents disagree. Am I
hearing things, or could he have said that? -- Diana

TOM: He probably DID say that, Diana. And good for you for paying attention
to this kind of stuff. Most kids in driver's ed just want to know how to
keep the rearview mirror from shaking so they can put on their makeup

RAY: Before we answer your question, we want to remind everybody that the
first thing you should do if your car is overheating is to pull over and
shut off the engine. You can ruin a modern engine by overheating it, so
it's best to pull over and stop if you possibly can. If it's not safe to
pull over for some reason, then using the heater might help.

TOM: Here's why. In the engine compartment, heat is dissipated by the
radiator. But if something is wrong, or the outside temperature is
extremely hot, and the radiator can't handle all of the heat, the engine
starts to do, what? Overheat!

RAY: So wouldn't it be nice to have an extra radiator for situations like
that? Well, it turns out you do. The heat exchanger (aka heater core) is a
small radiator that sits under the dashboard. And when you turn on the
heat, that little radiator takes heat from the engine and delivers it to
the passenger compartment.

TOM: It's not as big as the main radiator, so it's not as effective. But it
does take some additional heat away from the engine. And in an emergency,
it might provide enough additional cooling to save your engine.

RAY: The downside, of course, is obvious. If it's hot enough outside to
overheat your engine, it's going to be pretty darned uncomfortable inside
the car with the heat on full blast.

TOM: And, by the way, that's why there's always a can of Ban Roll-On in MY
car emergency kit!

Get the Car Talk Newsletter

Got a question about your car?

Ask Someone Who Owns One