There is something between the pulley and the body of the pump or solenoid housing, that's the only way it can lock up.

I would take the clutch off and investigate. YOu may not be able to actually repair it, but you should be able to get the pulley bearing fixed.

You would have to remove the AC compressor to get the non-AC equipped belt to work, and I don't know if MB ever actually sold that engine without AC.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!