It should not hurt it at all as long as it does not get up in the red. On one of my E300's I don't even have a fan shroud on it. It will get slightly over 100dC but that is all.

Something I've noticed on hi performance BMW's and MB's is that the radiator is only being used at around 25-40% capacity at 80 mph (based on cleanliness/newness, etc...).

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Jim