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Some pictures may help us. Sound like there's going to be fine plastic pieces in your coolant. I think Porsche designed these impellers to be fibrous because they anticipated this happening when a water pump fails. Better than having a metal impeller dig itself into the wall of the case.

I'd give that article a look-over. Then I'd flush my coolant and inspect it for those impeller pieces. I'm not exactly sure what you mean by a damaged crankshaft/crankcase? A picture of this would help.

A thorough flush and a new water pump should fix your problem.