The thing that controls the fan clutch operation is the bimetallic strip. Hit the junk yard and just get a bimetallic strip from a 400E or SL500. Those supposedly will flex sooner and allow the silicone oil to flow out and lock the fan up. I don't see how drilling and adding screws will change the temperature at which the bimetallic strip flexes.

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1990 190E 3.0L