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Q: Temperature problem

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When I start my truck the temperature needle will read cold for a good 5 min and then start to.jump around going.from a little high to a little.low. While driving on the highway it will hold normal temp with a very slight change. Would this likely be a temperature gauge issue or a possible leak?

My car has 165000 miles.
My car has an automatic transmission.

This can be caused by a number of things such as low coolant levels, a faulty thermostat, or a failing coolant fan switch. As you may know the coolant fan switch helps to maintain the proper coolant temperature by turning on and off at specific temperature thresholds. When this switch is not working properly, this can cause the fans to come on intermittently, all the time or sometimes not at all. When this happens you will notice a temperature spike and drop occasionally as the fan comes on and off. When driving down the freeway, the wind passing through the radiator will help to maintain a lower temperature. When sitting at idle, you may notice the temperature climb back up due to the lack of assistance of the fans or wind passing by the radiator. I would suggest having an expert from YourMechanic come to your home to diagnose your cooling system.

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