02 A4 3.0L Quattro, 89K. At first the issue was an engine coolant gauge that would stop working intermittently. A few days ago it stopped working all together, now have a CEL. When the car is in city traffic with little air movement I can actually see the outside temp gauge increase 5 to 10 degrees, it then returns to normal at highway speed. After driving home last night from work (30 to 40 minutes of highway driving) I could place my hand on the radiator. However, I was getting heat in the cabin. This leads me to belive that my thermostat is not opening up and allowing the coolant to ciculate into the radiator, hence the overheating at city speeds. Could this however be an issue related to why my engine coolant gauge stopped working, like maybe a faulty temperature sensor?

Any help would be greatly appricated.

Gordo.

 

if you scan the car then there should be a fault for your temp sensor if it's bad. Other then that it sounds like a thermostat.

 

https://www.audiforums.com/m_808550/tm.htm
It might be the coolant temp sensor, if it is, you have a chance for the free replacement by an Audi.

 

If the thermostat was stuck open coolant would always circulate throught the radiator and the engine probably wouldn't reach operating temp. If it were stuck closed, no coolant would circulate throught the radiator and it would overheat something fierce. If the radiator feels hot and your getting hot air from the cabin vents, its most likely a CTS failure.