DEAR CAR TALK: I have a 2005 Buick LeSabre. The only thing I've had to repair so far are the rear shocks. But one morning I started the car, and the needle on the temperature gauge was a bit past the center, which isn't normal. I took the car to a mechanic, and he said the problem might be something in the radiator, so he backflushed the system. This made the needle on the temperature gauge register a bit below the center of the gauge. After six days, the needle went past the center of the gauge again. I took it to another shop, and they checked the temperature, which was between 180 and 190. They replaced the thermostat. All was well for 10 days, but then the temperature gauge went into the red, "overheating" zone, which it had never done before. I was told that the 2005 Buick LeSabres were having trouble with the temperature gauge: The gauge shows that the car is overheating, but it's actually not. Can you figure out the problem? My wife is afraid to ride in the car.
-- Thomas
DEAR THOMAS: 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 gauge, and got a reading of 180-190. 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, 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.
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
DEAR TIM: Take it to a shop that has the same little device we have -- a small power pack that plugs into the car's data port. 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 you have set. 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 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 has ever listened to. So we hope it works for you, Tim.
Ray Magliozzi dispenses advice about cars in Car Talk every Saturday. Email him by visiting
cartalk.com
HomeStyle on 12/10/2016