coolant temperature gauge giving false reading

[Rob]

Hi. I own a 2003 hyundai sonata v6. My coolant temperature gauge is giving me a false reading. I had to replace the coolant temperature sensor to fix a different issue. Before I replaced that, I noticed my heat gauge would rise above normal temperature, but when I shut the car off and started it again a couple seconds after, it would be at the normal running mark. After I replaced the coolant temperature sensor, the problem escalated by showing an even higher temperature, reaching almost the red. I know that the reading is false because my scanner shows a constant 220 to 226f. Along with replacing the coolant temperature sensor, I replaced the radiator cap. Any suggestions on what I can do to resolve this issue? Thank you

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[96caprice]

When you change the coolant temp sensor, this opened up the coolant system and probably introduced air into the line. (remember how coolant came out when you removed the old sensor?)

air heats faster than water and is causing little hot pockets that the sensor is picking up.

I would bleed the system by running the vehicle cold with the cap open for a while until it warms up. make sure to put the heat on hot.

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