Just starting to hear odd..humming noise on and off. The temperature gauge will move beyond 1/2 mark..and move up to H mark..and say " turn engine off Immediately". Some days its okay, other days its not. Pump failing and/or thermostat sticking. I cant think of anything else.
Thermostat is faulty. Was replaced three years ago as part of a factory recall. Problem has resurfaced. Cost is ~ $1,000 because thermostat is located beneath the supercharger and replacement is "labor intensive."
While driving the thermostat sign appeared on my dashboard and smoke started to be seen on my hood. Had to park and have it towed to the nearest Audi dealer. The following day the dealer replaced a failing thermostat free of charge covered by my warranty. Just a hassle getting the fixed in between work.