[ohdee77]

I also own an Audi TT and just replaced its Audi oxygen sensor last month. There are many parts that may cause overheating. One of it is loss of coolant because of a leak. Possible leak points include hoses, the radiator, heater core, water pump, thermostat housing, head gasket, freeze plugs, automatic transmission oil cooler, cylinder head(s) and block. Check on these parts and do something about it.