Based upon my experience with the exact same issues on my '91 350SD and the advice given to me by the gracious folks here at the forum, those temperatures are definitely too hot - you run the risk of overheating and warping the aluminum head and then wrecking the motor; something you definitely want to avoid with these 3.5L's since they are already prone to rod bending.

I also just replaced both auxiliary fans up front, fan clutch, thermostat and refilled with MB Coolant. Now it consistently runs right around 80C - slightly above with A/C and slightly below without A/C.

I also agree that it was money well spent and would definitely recommend it.

__________________
Autos:
1991 350SD 276,000 miles
2001 VW Beetle TDI 115,000 miles

Horns:
1955 Selmer Mark VI Alto (55,xxx)
1958 Selmer Mark VI Tenor (85,xxx)
1964 Selmer Mark VI Tenor (125,xxx)
1967 King Super-20 Tenor (430,xxx)
2002 Selmer Series III Soprano

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