The 1.8 liter engine thermostat is located on the lower right hand side of the front of the engine. You can follow the top radiator hose directly to the thermostat housing.
The thermostat on a 1998 2.4 Audi a6 is located on the radiator under the top hose assembly. To access it, you will have to partially drain the radiator.
between the bumpers
You have to take off the front end of the engine, as if you were replacing the timing belt and water pump, huge effort for a thermostat.
Where is the electric radiator fan relay switch for a 2001 Audi A6 2.7t
If this is a 2.8 V6 the thermostat is located on the front of the engine. Ask 'Where is the thermostat located on a 1995 Audi A6?' on this site and you'll find someone has done a great job of explaining how to find and replace the thermostat.
18 Gallons
Low on coolant. Stuck open thermostat. Partially blocked heater core.
The EPA mileage estimate for the 2006 Audi A6 is 18 mpg in the city, 27 mpg on the highway.
The EPA mileage estimate for the 2009 Audi A6 is 18 mpg in the city, 27 mpg on the highway.
The EPA mileage estimate for the 2004 Audi A6 is 18 mpg in the city, 25 mpg on the highway.
The EPA mileage estimate for the 2008 Audi A6 is 18 mpg in the city, 27 mpg on the highway.
The EPA mileage estimate for the 2003 Audi A6 is 18 mpg in the city, 25 mpg on the highway.