Is my thermostat not functioning correctly..??

[METZGER]

Hi all, today was pretty cold 11 to 8 degrees C. I warmed the car up and and drove gently till it got to about 70 degrees. We went up a hill to a scenic spot but when we went back down the engine temperature got as low as 46 degrees... My thermostat must be stuffed? Because the heater wasn't as hot as it should be either so it's not like the temperature sensor is out... Couldn't give it the beans because the temperature is too low.. Just cause engine damage. And even the cars OEM temperature gauge showed 3 bars. I use the torque pro app to monitor the engine information. Looks like a big job to replace the thermostat too..

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[Rocketst]

The cars coolant sensor is infrared and grossly inaccurate. Did you have a crosswind while driving downhill? 8 degree weather plus an even colder crosswind would cause the radiator to cool very quickly. Also, if you notice before the car warms up even if you have the coolant at half like it should be until you actually get on the highway the car usually won't blow warm. Cars warmed up but until the engine oil and coolant warms up higher it's just not effective at heating the car. It sounds to me like your worried about nothing. It was just very cold outside and your radiator did its job turning cool air into cool coolant.

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[Snrub]

In my experience, the temperature gauge moves to 4 bars pretty quickly, even in well below freezing conditions. Based on all the information you've provided (OEM gauge, torque readout, heater blowing cooler air), I suspect your analysis is correct and you need to replace the thermostat.