I believe you may have just led me to the cause.

When I was trying to remove my alternator to address the charging issue earlier this year I bent that little strip of metal on the front of the fan. At the time, I briefly considered removing the fan/clutch assembly to give me more room to try to work on the alternator. I bent the strip thinking it covered a screw on the front of the fan...

I doubt I'll be able to bend it exactly into the right position...

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Daily Driver: 02 E430 4MATIC
In the family: '03 E500 // '04 ML500 // 64 220SE