I have a 2005.5 Audi A4 2.0T Quattro which is the B7 model and I recently been having small problems with the car. My fan has been over working itself lately like never before. Also, last night my car kept over heating but I kept the temperature stable by putting the heat on in the car towards the dashboard and all the way up on blast. It definitely controlled and stabilized the temperature for temporarily. As soon as I accelerate the temperature rises and over heats. Could it be the thermostat? I don't think the hoses are circulating because one of them are hot and the other one is cold.

 

could be the thermostat, could also be the water pump. has the coolant level dropped? if not, then i'd replace the thermostat first. if that doesn't work, i wonder if the pump is shot or not working 100%.

always use OEM fluids as well.

 

I'm just curious..how many miles do you have on it? Do you have a CEL indicator on? If I am not mistaken, a thermo issue or temp sensor will trip a P0128? Guys, feel free to chime in on that. If you are approaching 100k, I would probably look into going ahead and changing out your timing belt and water pump just for extra insurance but be prepared..it cost me $800 at my indie, or $1400 at the dealer to do both. With you saying that one hose is hot, the other is cold...and that it is a 2005.5, and you don't have a CEL, my gut is leaning towards the water pump. BUT...if you can crawl under and change out the thermo yourself...it may be better to start with that since it's a cheaper fix...

 

If your lower hose is cold, your thermostat isn't opening. As asked, what kind of mileage and service history do you have? And also, if you're in the NE, I can handle the diagnostics and repair if you need it.