My new aluminium motor was fine on the road, but got hot when subjected to stop and go traffic. I kept the puller fan and had a custom radiator shroud fabricated and installed. Then I dumped the ethylene glycol and replaced it with distilled water and Water Wetter. The overheating disappeared, although I do try and avoid heavy traffic when possible anyway. My beast is fortunate to live in a garage in a very temporate climate, so freezing isn't a worry. Life is good.
Rich