On 11/12/2017 17:47, Cynic wrote:
Presumably you mean the shaft is spinning. There's no guarantee that the impeller is.
Grundfos pumps had a nasty habit of shearing the shaft at the impeller end.

Indeed, that was one of my thoughts too but if I whipped that off and it
was OK I've delayed the repair even longer and at the moment I don't
have time to tinker & fix.