Low coolant level in reservoir! Called in to my dealer and a leaking water pump was the cause. The car will be a year old on 28 March and has done just over 27k miles. It's the second water pump replacement they will have done on A3s. They will change the cam belt at the same time. I'm driving an A4 2.0 TDI Quattro as a courtesy car until its done on Tuesday! edit..don't know why a link has been created from A4 text above?!!