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Q: Temperature gauge is rising but reduces to normal when the heater is put on full blast

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I think the Coolant level is low, can I just add water to the Coolant tube as a temporary measure

My car has 100000 miles.
My car has a manual transmission.

This may be caused for many different reasons such as low coolant level, a faulty thermostat, faulty coolant fan switch or potentially a blown head gasket. When the heater is on, this tends to pull heat away from the radiator as this is part of the function of the heater core and is what heats the cabin of the car when the heater is turned on. This suggests you have some kind of cooling issue related to any of the above. Adding water to the radiator may very temporarily solve your problem, but will likely not last long depending on how severe the problem is. I would recommend having an expert from Your Mechanic come to your location to properly diagnose and inspect your cooling system.

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