I have replaced the useless aux front fans on my W210 with a high performance electric fan which is thermostatically controlled. I might remove the viscous fan at some point but the electric fan kicks in every now and then usually when stuck in traffic on the motorway.

If you get worried about the cooling at any point and need to dump some heat (say if the temp was getting way too hot), max out the heater to fully hot and perhaps change the air direction to your feet so you don't roast. The heater matrix will act as another radiator with fast moving electric fan.

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UK spec Mercedes W210 E300 Turbodiesel wagon - OM606.962 with 722.6 transmission - rust free!