Erratic turn signal operation can be a result of a failing turn signal flasher relay which will require replacement.
2000 Audi TT Quattro Problem Reports
Most Reported 2000 Audi TT Quattro Problem Reports
A creaking type noise may be noted from the front suspension. Replacement of the front sway bar may be required to correct this issue.
The water pump may fail resulting in engine overheating and possible timing belt damage. Overheating and/or timing belt failure can result in very expensive engine repairs. As a precaution, it is recommended to inspect the timing belt and water pump at regular intervals.