A few months ago my rear coolant flange blew out. It got replaced, and since my car's temp gauge keeps going into the red for maybe a minute, then back down to halfway, accompanied by the annoying coolant warning.

My coolant is fine. There is no air in the lines. The Audi dealership has flushed my coolant three times and filled. Even gave me my own gallon of g12 free of charge in case anything happens.

Audi also replaced my water pump and thermostat and after a few weeks, the damned thing is doing it again. Usually when going up hill on chilly days (being in Wisconsin, lucky for me the weather doesn't know it if wants to be 40 or 70 this time of year)

So I come to you guys to hopefully give me some insight. The only thing I haven't changed is the coolant temp sensor which I was told by Audi wouldn't effect the reading of the temperature gauge.

I'd like some sort of idea to bounce off of the tech before bringing my car back yet again to the dealership.

Thanks in advance and for reference, it is a 2003 1.8t.

 

Audi also diagnosed that my heater core is broken, also said that isn't the problem with my car falsely saying its overheating.

Thanks again. Hopefully someone can help.

 

Shameless self bump