2010 Aveo temp gauge fluctuating

The temp gauge on my 2010 Aveo LS keeps jumping up to about 3/4 and then within 5 seconds goes back to normal temp. It also starts running cold and then returns to normal in the same fashion. This happens only after the engine has been warmed up fully. All fluid levels are full. Also the car has trouble starting when cold. It takes 2-3 tries to get the engine to kick over and once it does start it initially stumbles. Took the car to a mechanic and they think it might be the head gasket but want to run some tests first to confirm. Anyone have any idea what might be the cause of the problems? Car has 40000 miles on it.

I don't understand how a head gasket is suspected, after you told the guy all the fluids continue to be at normal levels, and it's running ok when warmed up. First a disclaimer that I don't know very much about the computer controlled thermostats on the newer Aveos. That said, if it were mine I would hang on a new temp sender, which appears to be an easy part to replace in the T-stat housing, and costs $20 or less. Up and down cycles fits in with a bad sender. And if the sender is incorrectly telling the ECU that it can close the loop, that could explain why it's having problems starting when the engine is cold.

Mechanic confirmed the head gasket is blown. How common is it for a 2010 with only 40000 miles to blow the head gasket? I bought the car from a dealer only a month ago and was running fine until the temp gauge started fluctuating.

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Originally Posted by mhoshii

Mechanic confirmed the head gasket is blown. How common is it for a 2010 with only 40000 miles to blow the head gasket? I bought the car from a dealer only a month ago and was running fine until the temp gauge started fluctuating.

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But you said all fluid levels and quality were ok. I'm having trouble figuring out how none of the fluids are affected if it's a blown HG. But if it is the HG, then what is the powertrain warranty for a 2010?

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Originally Posted by avguy

But you said all fluid levels and quality were ok. I'm having trouble figuring out how none of the fluids are affected if it's a blown HG. But if it is the HG, then what is the powertrain warranty for a 2010?

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its a 5 year/100K Powertrain Warranty, and it covers pretty much all the mechanical parts of the Engine and Transmission only; if you have an electrical/electronic problem, you are pretty much up S(*&T Creek without a paddle; as the electrical/Electronic parts are only covered by the 3/36 Bumper to Bumper Warranty, and the PCM and Cats are covered by the 8/80 Emissions Warranty. and to the OP, did you buy your Aveo used, because I have a feeling that your engine has been abused; because I have the same Model Year, with 69,218 miles on her; and besides a bad O2 Sensor that I need to replace, she runs like a little Metronome despite being a Former Enterprise Rental Car!

Hey there mhoshii,

I’m sorry to hear of this concern with your Aveo. I will be glad to look further into this concern for you. Was the mechanic you took your vehicle to GM certified? Please send us a private message if we can be of any extra assistance. Thank you.

Kristen A.
Chevrolet Customer Care

Hard to start and temp gauge fluctuating signals a bad coolant temperature sensor. If it was the head gasket, you would be loosing coolant.