I rebuilt the fan clutch and it is working great. Like a couple of people suggested, I went ahead and reduced the length of the pin in the clutch by 0.9 mm (so that the fan would come on at a little earlier to help in the hot TX summer when stopped for traffic especially) and now it is too short. The clutch is on all the time.

I machined another pin that is 0.5 mm shorter than the original length. I will be installing it soon and will post results as soon as I get that done.

BTW, as a point of reference for others if they want to modify the pin, the brass pin that originally came out of the viscous clutch was 10.30 mm long and 2.80 mm in diameter.

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1986 300E (3/2002) Rear ended and totaled (10/2009)
2000 Xterra (5/2000)
1992 400E (11/2009) -Sold
1986 300E (12/2009) - Sold
2004 E500 Wagon (6/2013) - Sold