I couldn't find that slot on my M111 (4 cylinder 16V engine), used a pipe wrench on two of the four bolts on the water pump pulley to hold it all. Fan clutch is a left hand thread on mine, the manual didn't say that!

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Mick J
'08 Chrysler 300CRD (MB OM 642 engine)
'95 E220 estate
'89 230TE (R.I.P.)