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Q: Temperature gauge going up and down

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My temperature gauge goes up to about. 3/4 then when I turn on heat takes a little bit to go down but it comes down . lately its been hopping sooner after I drive then before . not sure if it the. Thermostat cause I have heat..please help

My car has 139000 miles.
My car has a manual transmission.

Hi there. The issue is the thermostat. It is sticking about half way and not opening all the way up or it has a lot of calcium buildup. I recommend replacing the thermostat and flushing the coolant out and putting in new coolant of 50/50 mixture. If you need further assistance diagnosing your coolant issue, then seek out a professional, such as one from YourMechanic, to help you with your vehicle.

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