I run two Marineland 350's and love em. Try this - unplug cannister, unlatch from base, and carry to sink. Remove all innards and clean. Rinse out down the slot where the impeller sits. Feel the magnet of impeller for imperfections. If you find any grooves or burs then order a new impeller. Improper maintainance can lead to carbon grains getting into base. Once cleaned and impeller ready then reload. When you reload the carbon do not fill past 2/3 - 3/4 level. The carbon expands as it gets wet. Rinse carbon dust out with tap water. Replace blue sleeve material. Put back together making sure both gaskets (flat) are in place above and below the carbon cartridge. Align and drop into place. Before putting top on make sure valves are open and top gasket seal are in place. Align it and flip over the four latches. Use aquarium water poured through top hoses to fill until water comes out of other one. Close valves and carry back to base. Hook up hoses and open valves then restart. It should run immediately and quietly! If not you have some other mechanical problem. Usually the impeller is the only week link in the system. Good luck!
