whenever your car is close to overheating you want to turn on the heater to max as soon as possible as that usually helps to cool the coolant. the heater matrix is nothing but a small radiator.

as for damaging your engine its possible.

you should be paying more attention to your instrumentation and making sure you
a) have good oil pressure
b) are not close to over heating (near or above 100 mark)
at all times.

__________________
'O=00=O'
bmw 2002.
long live the legend