Hi, I have Audi A3 2.0 TDI (140) 05 plate. I was in London other day and got stuck in horrerous traffic barely 100 yards per 5 min! I even had gearbox in netural position, handbrake on when not moving and its suddenly went to 100 degree even its had a proper coolant liquid in and on maxmium level. Mind you that day was about 30 degree outside! When its got 100 degree and I put full heat on and its went back the normal temperature (middle. 50 degree if I remember correctly) then switch heat off its did happened again but when I am moving such as got out of London and its was on right temperature (middle) and never got overheating again. What fault could be for this? I am just concered as I don't like damaging my engine.