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Q: Coolant boils, not sure if overheating.

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parked car and noticed radiator fan still on. Popped hood and coolant reservoir was LOW. Next morning, added 50/50 mix to reservoir to MAX fill level. Drove around neighborhood. Coolant in reservoir steaming out from cap. Shut off engine, and reservoir went back to low. Used infrared thermometer to measure radiator temperature. 210 degrees at top, about 100 at the bottom. Water pump and rad. cap was replaced 6 months ago. Heater blows heat. Not sure if Tstat is faulty, water pump faulty, or a blockage in Radiator.

My car has 80000 miles.
My car has an automatic transmission.

Hello. It does sound like a thermostat issue. If the thermostat is not opening as it should then this will occur. It also sounds like the radiator cap may not be holding pressure. I would typically test the thermostat and the radiator cap to see if they are failing and replace what is needed. From your findings I would say it is a good idea to start with the thermostat. If you want to have this repaired, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose this and replace your thermostat if necessary.

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