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Q: Coolant Temperature Gauge

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I have a 2007 Audi Q7 Premium 4.2 Engine. My temperature gauge is extremely slow to reach operating temp even after driving. I changed the coolant temperature sensor with a auto parts store sensor it helped briefly. Could this be because I need to use dealer oem part in Audi or a bad Tstat? Also the fan does not kick on to cool the engine after driving

My car has 106592 miles.
My car has an automatic transmission.

A: Hello. This potentially sounds like a combi...

Hello. This potentially sounds like a combination of a faulty thermostat that may be stuck open and possibly a faulty coolant temperature switch that is causing the cooling fans to not come on. For a more precise diagnosis, I recommend having a local expert, like one from YourMechanic, to inspect the cooling system in order to have this correctly addressed.

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A: This problem is likely caused by a failing ...

This problem is likely caused by a failing thermostat. The thermostat is designed to restrict coolant flow to the radiator until the engine reaches designed working temperature (something close to 210 degrees Fahrenheit). Getting to working temperature faster is important for fuel efficiency, lower emissions, better flow of oil within the engine, faster "time to heat" for the heater, etc. If the thermostat is not allowing the engine to reach, and stay, at designed operating temperature, the auxiliary fan will not turn as well; since it's activated by the engine reaching a certain temperature. I would recommend a Thermostat Replacement service which would be performed by a certified technician from YourMechanic. This will allow the confirmation of a diagnosis, and to give you a better idea for repairs.

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