I just tore mine out this week after three years and about 120 hours. One thing stated is that the impeller can take a set and not pump efficiently because it doesn't straighten out to create the vacuum necessary. I did notice that the vanes were curved when I removed them from the housing. In addition, when I replaced the pressure valve (HPDI) I found a piece of broken O-ring which I assumed was from the pump. After removing the pump, the large 0-ring was torn and pieces were missing. Fortunately, I used a gasket sealant on the housing to the plate seal and it did not appear to be leaking. I would probably just replace the impeller as the bottom plate and metal housing looked brand new. If you have time, remove it and then replace just the parts that you think you need. SIMYamaha is a great resource. Cost was $80.00 for the deluxe kit. The impeller alone is $25.00 I feel that if you are replacing regularly, you don't need to replace all of it. I am sure others will feel differently. I feel it is also good just to disassemble these parts so that when you need to, you can.