Canister filter noise - water in the motor?

[Callatya]

I have a love/hate relationship with my canister. It is a VA 650 Professional, old model that has been superseded by the CF1000.

It has fantastic oomhp and great media room, but is a bigger to prime and it is a little rattly, and lately the rattles have increased. usually it is just a matter of getting a little bit of biofilm on the impeller and rejigging the bioballs so they don't bounce around.

I have packed and repacked it. I've checked the impeller and housing, I've wiggled out all of the air bubbles, and still it is rattling and grinding away. It is getting worrying.

It doesn't sound like media when you get up close, it sounds like the motor. It is like a toned down version of the put-put you get when you first start up an outboard, but with more rattle.

I have had a look at the motor section. I opened it up and discovered that the motor itself seemed to be fully encased in a black box. It looked to be resin-filled, presumably to stop water getting in should water find its way into the top section (which it now is for some reason). The whole area seems intact.

Can anyone help me out? What should I be looking for here? Is there a seal in this area that might need looking at? Am I way off track?

[Stuart Elflett]

Most canisters CAN be overhauled - some supply parts so you can do it yourself, others need to go to a shop... without hearing the noise, I'm just guessing - it could be cavitation from an air pocket, it could be worn bushings in the motor - I've had several pumps go noisy just from plastic guides simply getting too worn... make sure the impellor is being properly and tightly held in place at both ends - if not, it'll get noisy... that's pretty universal, and one of the first places I'd look - I have an internal pump under my desk that I know has a dodgy impellor mount on one end, borrowed from eheims range because parts weren't available for this brand...