Car Talk

DEAR CAR TALK: I've been driving cars for far longer than I'd like to admit, and I've never had this happen: I drove a few miles to the market in my 2004 Jeep Grand Cherokee, and normally by the time I get there, the temperature gauge has climbed to where it should be. This time, it got only halfway there. It was in the same place by the time I got home. The next day, I drove about 70 miles, and the same thing happened. Only when I sit at idle for a few minutes (maybe four to five) will the needle start to climb a bit. But once I start driving again, down it goes. Now, I've had this car overheat a few times (I needed a new thermostat), but never have I had any car stay cold. What's the deal here? Is it OK to keep driving it? And how expensive do you think it'll be to get it back to normal?

-- Catherine

DEAR CATHERINE: You may need another new thermostat.

Your old thermostat failed because it failed to open -- and therefore to allow coolant to flow through the radiator and cool off. Your current one may be opening too early, or may be stuck open and allowing too much cooling. That's the most likely explanation for a car that runs cold.

It's OK to keep driving it for now, but the reason thermostats exist is to regulate the engine temperature, because engines tend to run most efficiently at right around 200 degrees.

So don't be surprised if your mileage drops. Although on a 2004 Grand Cherokee, you might not notice the drop from 12 mpg to 11.

Start by having your mechanic verify that your gauge is accurately representing the temperature of the engine. He'll do that by using his own pyrometer to check the engine temperature.

If the engine is actually running at a normal temperature while the gauge says it's cold, then you may need a new gauge or a new temperature-sending unit.

But if the gauge is accurate, and the engine really is running cold, then I'd change the thermostat and see if that fixes it. I'm guessing that's all it is, and thermostats are cheap.

DEAR CAR TALK: If you could help us figure this out, we'd appreciate it soooo much. During the summer, we love to sleep with the windows open for fresh air (in the house, not in the car). But every night, we are disturbed by a very rapid horn at a high pitch going "beep beep beep beep beep beep" at least six times (my husband hears seven beeps) in the space of 1 second. It scares us both awake every time. We live in a dense, otherwise quiet neighborhood with small lots, so there are lots of potential culprits' vehicles parked around our home. Do you know of a vehicle security system or other weird thing that could be malfunctioning? We're pretty sure it is an involuntary thing on this car, and not triggered by the owner's key fob, because no cars drive off and no doors are slammed shut afterward. Any ideas? We'd love to chat with this beeping-car person. Thanks a bunch.

-- Cheryl

DEAR CHERYL: I think it's an alarm system that's being armed by the driver's key fob.

One of your neighbors gets home very late, and gets out and closes his car door, which you sleep through. Then he uses his key fob to lock the door, which triggers the "alarm is armed" sound, which wakes you out of your dream about Matthew McConaughey.

Fortunately, most factory-installed alarms can be programmed to not sound the horn or the alarm chirp when activated. They often can be programmed to do nothing, or to just flash the parking lights to let the owner know the car is locked and alarmed.

So you're going to have to do some detective work and figure out who the culprit is, so you can ask him to reprogram his alarm!

I'd employ some modern technology. You want to get a webcam; they're cheap these days. People use them to spy on their dogs while they're at work now, so they can come home and say: "I know you got into the garbage, Huey. I saw you on the webcam." As if the tipped-over garbage can with the week's worth of garbage strewn all over the Oriental rug isn't enough of a clue.

Anyway, I think you should set up this webcam on your front porch or in a street-facing window. Point it in one direction one night, and in the other direction the next night. See what you catch. Most alarm systems do also flash the car's lights when they are engaged, so you should be able to see it.

Then you need to leave a note on the car and hope the owner is a humanitarian.

Hey, who knows? Maybe he's trying to sneak home after carousing late at night without waking up his wife, and he'll be thrilled to know he can silence the car, too.

Ray Magliozzi dispenses advice about cars in Car Talk every Saturday. Email him by visiting

cartalk.com

HomeStyle on 09/26/2015

Upcoming Events