I have an Eheim Ecco Pro external canister filter on one of my tanks. It's been running for years and has run flawlessly.....until a few nights ago when it started making clicking noises. With canister filters, such a noise is invariably the impeller. So I removed the pump head, turned it over, and unlatched the impeller unit cover (called the pump chamber). I visually checked the impeller to ensure it was seated correctly. I knew there couldn't be a foreign body of some kind caught in the impeller because it would be impossible to get there. I prefilter the intake with a high density sponge, which will stop anything the size of a grain of sand or larger. Everything looked fine.
Next, I removed the impeller unit from the pump head and inspected it. The impeller unit for an Ecco is actually made of three parts - a cylindrical magnet, the plastic fin blade, and a plastic insert that the impeller blade slides over and which fits into the center of the magnet (see the photo below). I immediately noticed that the plastic insert had pulled loose from the magnet by about 2 mm. The plastic insert has four notches at the base where it meets the magnet and the magnet has grooves in which these notches fit. If the notches line up with the grooves, the base of the insert will fit snugly against the magnet (as pictured). If the insert has pulled loose and rotates just a bit, the assembly won't fit back together cleanly.
Whatever adhesive that had been used to connect the insert with the magnet had failed, allowing the insert to pull free from the magnet. It can't be pulled too far apart once in the pump chamber because there is a round, plastic shaft that goes through the insert and through the magnet. This shaft goes all the way through and snugly fits into a round hole in the pump head. This shaft is what holds the impeller unit in place and allows the unit to rotate.
Unsure whether I could fix the unit or get a replacement quickly. I ordered a new Ecco (my lfs doesn't carry them). However, I had to run to my lfs for some other items, so I took the impeller unit with me. I showed it to the store manager, who looked at it for about a second and said, "Follow me." With that, we headed back to their "maintenance" room where she grabbed a little tube of Loctite liquid super glue and proceeded to glue the plastic insert back to the magnet. She said, "that'll do it." Concerned about the chemicals in the super glue, I asked "are you sure about that?" She explained that the super glue is completely inert once it dries. She said "we use it to fix all sorts of things including artificial corals that have broken."
I had no idea.
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