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Q: Temperature gauge goes up when driving and down when not

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We got on the freeway and noticed that the heater wasn't working and the temp guage was getting hot and went all the way up we pulled over and put antifreeze in and made sure there was oil. When we would drive it would go up when we stopped at a light it would go down. We noticed antifreeze had leaked out somewhere under the hood probably when it went to hot.

My car has 199000 miles.
My car has a manual transmission.

Hello. This suggests you may have a faulty coolant fan relay switch. This is a relay that triggers the cooling fans to come on at predetermined temperatures. When this is not working properly, this can cause the fans to come on intermittently, all the time, or not at all. When they do not come on at all, this will cause the motor to get hot, especially while sitting at a stop since there is no air flowing past the radiator or engine. As you speed up, the air from the speed of the wind will cool it down slightly which is what you notice when your gauge drops. I would recommend having an expert from YourMechanic come to your home to diagnose the overheating issue and let you know what needs repair.

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