I've seen this before -- leaking front seal causes the rubber insert to fail, so that the outer ring of the clutck that actually contact the pulley isn't connected to the inner part that turns the shaft.

You will need a new clutch and to replace the seal. This can be done in the vehicle with the proper tools (pin wrench to hold the clutch, although if it's torn, you will have to find something else) and the tools to R&R the seals.

Or you can pull the compressor, take the front section off, and replace that o-ring and drive the seals out and new ones back in.

This isn't difficult.

The black stuff is the rubber in the clutch.

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!