Hi guys got a 1.9TDI Elegance '06 with 89,000miles.

Strange situation today, I am a driving instructor, and after 1hr lesson with ac on, 25% by road talking, couple of stalls etc....

Cooling fan went nuts....started racing.....odd....suppose ac is on, and we are in sun, engine @ 90' - Fine!

Getting student to reversing into space at home, cloud of grey/black smoke from under engine. got student to stop and turn off. Checked everything no issues!?

Fan still going, waited for it to stop. Drove fine, turbo fine, power good, ac fine! ?

Dunno whats' up?

Very strange. Can only assume fluid of one type or another hit engine and burnt off. All you can do is check all fluid levels, and keep an eye on things.

One thing to check, is there any oil around the EGR valve and inlet manifold? The EGR can leak with age, and with heat soak due to sitting still for too long, the oil may start to boil off.