RAY: The first question to answer is, Is the car actually overheating, or does the gauge just say it's overheating?
When you went to one of the mechanics, he measured the temperature, presumably with his own gauge, and got a reading of 180-190 F. That’s perfect.
Since the gauge went into the red zone after that, I would do that test again. We have a pyrometer at the shop, which is an infrared temperature gauge that we can point at any of the coolant hoses. It’ll tell us the temperature of the coolant, independent of what your gauge is saying.
If the engine actually is overheating, then you’ve got a serious problem. It could be anything from a bad water pump or a leaky head gasket to a cracked cylinder head. Let’s hope the coolant reads 190 again, which means the engine is just fine.
If the engine is running at its proper temperature, then the problem is in the system that monitors and reports the temperature. It could be a bad gauge, as you suggest. But before you rip out the dashboard and pay for a new gauge or instrument cluster, I start by replacing the temperature sending unit (TSU).
The TSU reads the coolant temperature in the engine and sends that info to the gauge. The TSU is a $40-$50 part, and no big deal to install. If that fixes it, you’re all done and your wife will ride with you to the rock-climbing gym again. If a new temperature sending unit doesn’t fix it, then go ahead and replace the gauge.
But if you’ve been kind to strangers and flossed regularly, all you’ll need is a temperature-sending unit, Thomas. Good luck.
How to keep presets during battery change
Dear Car Talk:
The battery in one of my vehicles is nearing the end of its life. What is the best way to preserve the electronic presets (radio, lights settings, etc.) when the battery is disconnected during replacement? – Tim
RAY: Take it to a shop that has the same little device we have, Tim. We have a small power pack that plugs into the car's data port, and when the ignition is off, it trickles a small amount of power to the car's computer.
That way, while the battery is removed, you keep your radio presets, your clock and any other memorized customized seating, door-lock or lighting preferences that your car allows you to set these days. Your computer also will retain the car’s performance parameters.
Lots of cars these days “learn” your driving style and set things like transmission-shift points based on that. The computer also stores sensor and emissions data that you’ll need when you get your car inspected.
Granted, it doesn’t take more than a day or two to re-acquire that information, but it’s one more benefit of maintaining minimal power during a battery change.
Most shops will have one of these devices. And if you want to, you even can buy one yourself. I’ve seen a “home” version for about $20 that runs on a 9-volt battery and plugs into the car’s cigarette lighter. Then you can be known throughout the neighborhood as the guy who saves radio presets.
I will warn you that it works about 95 percent of the time. For some reason, it fails occasionally, and then we have to set all of the customer’s presets to NPR and convince him that that’s all he’s ever listened to. So we hope it works for you, Tim.
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