could be the coolant fan not cutting in when it should ( fuse/fan switch/relays ) you could run it till the fan cuts it to confirm this

 

Actually they are in the habit of using the plastic ones. That was the most frustrating thing about trying to find someone here in Colorado to do it. The dealers here only use the Audi part which is plastic and I couldn't find a shop that was reputable to do the job before I had it done (found a great shop literally the day that the dealer completed the work on my car which I will use from now on.)