Thanks again. I haven't heard from the dealer yet, they are still researching, so this is very helpful. It hasn't happened again. Weather is less cold (relevant?). I have been in very heavy traffic and jams, driving in 1st or 2nd gears for 30 minutes or so, and it hasn't overheated. In fact the temp gauge behaviour and reading look pretty plausible all other times. I'll still check the fan kicks in when iddling. Thanks!