[Goran]

I am having the same issue. Although I have a known bad coolant temp sensor, so that could be it in my case.
I thought the viscous fan needs to engage at certain temp? Its always idling but not full force until the clutch engages. I remember there was a simple check to test it, if you can stop it with a pen then the clutch hasnt engaged.

Just to add, from experiences with my previous S8 it should not overheat even in really hot weather. I took that one all over Europe, down to Morocco, and to central Spain when temps were over 40C, the gauge never went past 90. So to my mind something is not quite right with my current 8