Hi
Sorry this is a bit long winded, but here is the story.
My 1997 Audi A4 2.6 V6 auto (136K miles) had always run at a consistent 90 degrees on the temperature gauge no matter what! Then intermittently it started to run a little hotter and after checking around the engine I noticed that the reservoir bottle was cracked and had a very minor leak so this was replaced and the fluid topped up. The temperature was still at times hotter than I expected but everything seemed to be working fine (the heater was blowing hot when required and the AC was cold when selected).
Then out of the blue the car completely overheated – the temperature was right off the gauge and the warning chime and dash light came on. I immediately took the car to a local garage who over the next 24 hours changed the thermostat and the coupling (I think this was the viscous) which seemed to cure the problem (the water pump had already been changed at (118K miles) when the timing belt was replaced).
The weather at the time was fairly cold and I had the heater on and the temperature seemed to be okay again at around 90 degrees (the middle of the gauge), but then the weather got hotter, I turned the heater off and the car started to run much hotter at about 100 to 105 degrees (you can hear the second (electric) fan coming on when the temperature eventually gets to about 110 degrees but it does not seem to cool the engine down very quickly – it also does not seem to run on after the engine is turned off).
I took the car to another garage that changed the temperature sensor (in the radiator) and replaced the fluid with branded Audi D12 (pink) just in case the first garage had not used the correct stuff but still the car runs much hotter than before and smells hot.
I have also noticed a very strange problem when I turn the heater on after it has been off for a while as it makes my windows go dirty around the front vents (like they have been cleaned with a dirty cloth) and a couple of times I have noticed a mist coming out of the vents.
Finally, the car seems to warm up much quicker than before and gets to 90 degrees very quickly, it sits at 90 degrees for about 8-10 miles before the temperature creeps up but I can reduce the temperature by turning the heater to full blow. The car does not actually completely overheat, I am not loosing any fluid and the engine runs like a dream (no indication of a head gasket problem).
Maybe the radiator needs to be changed or the heater matrix/core, but as it is a fairly old car now I do not want to just keep spending out without some knowledgeable instruction – does anyone have any thoughts or ideas? Any help would be greatly appreciated. Thank you.
Similar post with no answers here:
http://www.audi-forums.com/b5-forum/47274-hot-not.html