Click & Clack: Don’t fall for this song and dance

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Updated: January 31, 2012 4:23PM

Dear Tom and Ray:

I had a heater core on a 1999 Dakota Sport replaced, and I now have heat all the time without it being turned on. I was told that I was feeling heat from the engine because there is no insulation on the fire wall. I didn’t have this problem before the new core was installed. What, if anything, did they forget to do? — Greg

TOM: Boy, you’re an understanding guy, Greg. They give you a song and dance like that, and you say, “Okey-dokey,” and walk away. We could use some customers like you!

RAY: That’s not heat from the engine bleeding through, Greg. That’s heat from the heater. And it’s likely the fault of the guys who changed the heater core.

TOM: But before we conclude that they’re absolutely to blame (we’ll get to that soon enough), let’s look at one other possibility. The heater controls in this truck are operated by engine vacuum. There’s a check valve under the hood that helps the system maintain vacuum during hard acceleration.

RAY: Right. So if that check valve were broken, your blend doors (the flaps behind the dashboard that regulate how much heat comes into the cabin) can pop open during hard acceleration.

TOM: So if you’re getting a surge of heat only when you’re accelerating hard or climbing a hill, then this five-dollar check valve could be the problem.

RAY: But if you’re getting heat all the time — which is what you say in your letter — then these guys screwed something up. Maybe they jammed a blend door so it can’t close all the way. Or maybe they forgot to reattach a vacuum hose.

TOM: The reason they’re trying to get rid of you is because rescuing the Chilean miners was easier than getting to the heater core in this vehicle. They don’t want to do it again. For free. So they’re hoping you’ll just go away or start driving around in your bathing suit.

RAY: So you’re just going to have to be a little more insistent when you go back to see them, Greg. Bring a couple of large friends with you. Or a lacrosse team.

TOM: They don’t want to take out the dashboard again, but that’s what happens when you screw something up — you have to do it again until you get it right.

RAY: Sure. Ask my brother about his years in eighth grade.

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Wait! Don’t buy another car without the mechanic’s checklist that’s included in Tom and Ray’s pamphlet “How to Buy a Great Used Car: Secrets Only Your Mechanic Knows.” It will help you get a good used car and avoid the clunkers. Send $4.75 (check or money order payable to Used Car) to Used Car, P.O. Box 536475, Orlando, FL 32853-6475.

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Get more Click and Clack in their book, Ask Click and Clack: Answers from Car Talk. Got a question about cars? Email Click & Clack by visiting the Car Talk website at cartalk.com.

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