My brother in-law's A8 has an overheating problem after the "quick fix" of the oil cooler pipe leaks- He poured the radiator leaks sealer into the coolant in the attempt to seal the leaks-The thermostat stops opening, stuck close. We don't know if the thermorstat ceased to open on its own or with the help from the sealer-The bottom line is the temperature will operate normally @ 1 mark before the red... Too hot. We decided to check the thermostat and replace the oil cooler plastic pipe at the same time. The oil cooler will be another write-up.

The timing belt is like new, so we don't want to change it at the moment, but if the timing belt is out, it will be a lot easier to do. The 40V thermostat is behind an aluminum cover (manifold?) and behind the timing belt which makes it extremely hard to replace, unlike the 32V which placed by itself and very easy to replace. Many people did this without removing the front bumper and pull the radiator assembly out to have more room which I think it's not efficient. It only took less than 30 minutes to remove the bumper and the radiator...