I picked up a 2001 model 2.0 Mark 4 GTi 3 days ago. The first 24 hours were fine, then the heater started pumping out hot air, then on the way home from work, the engine overheated .....but bizarrely didnt show any sign of overheating, ie steam or mayo like substance and there is plenty of coolant in it. Any ideas ?? Could a change in the style its being driven in effect things ??