1987-420SEL with 169k miles

I've noticed in the past few weeks that the viscous fan clutch is engaged nearly continuously at freeway speeds with ambient temps above 60F. Between 50-60F the clutch will cycle on/off every couple minutes cruising @ 60mph. Below 50F the clutch stays disengaged. Engine temps are ~82C on cool days, ~85C on warmer days when clutch stays engaged all the time. I've always use MB antifreeze since I got it in May-2005.

Seems like the fan clutch is working right, do I need a new radiator?

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Matt
Seattle, WA
87 420SEL
83 300D
69 Dodge Charger
64 GMC C10 truck