Where is the thermostat located on a 2000 Audi A6?

the thermostat is located behind the waterpump, its kind of a big job to do. if you can find someone to do it, try to find a failsafe thermostat. A failsafe thermo is a thermstat that if it goes bad it will go bad in the open postion. its about a 1000 dollar job, so if there is a problem again, at least you can still drive the car.