Ducati MONSTER 821 Workshop Manual page 845

Slide out the water pump cover and collect the two bushes (5).
Clean the pump housing from any coolant scale. Check the bearing wear by turning the impeller shaft (6);
in case of excessive clearance, it is necessary to replace them as follows.
Remove the snap ring (7) from the impeller shaft, and the washer (8) underneath.
Slide off the impeller (6) with the sealing ring (9) from the outside.
Collect the ceramic washer and the seal ring unit (14).
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