Bummer, sorry it didn't work. When the coil (motor) gets gunk in it I use a q-tip to clean out the impeller chamber. But for me anyways, it's more reduced flow than noise when the impeller gets gunked up.
Are you in contact with AC
's helpdesk? They stand by their products and may have a better solution.
If you decide to trade brands, check out Fusion power filters. I have one, a 40 (along with the AC50) on my 37 tall and it works great.
Hope you can resolve it and please keep us updated.
Sent from my Epic 4G