You might try replacing the clutch with a solid mount fan from a 240d.

For the record, on the MB vans with the 616 and 617 engines, the fan clutch comes with a metal tab which is designed to be bent if the clutch fails. It locks the clutch up and turns it into a direct drive fan. The manual does state a limit as to how long the engine can be driven that way. Can't remember what the limit was.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13