Hi I am going through the same issue right now. Aquaclear70 that 3 months old. I gave the filter a good cleaning last night, either than filter media cleanings, this is the 1st one it's had. I even took out the impeller for the 1st time, and took a paper towel and wiped off the crud from the magnet and its fins, and gave a shot of water in the impeller cavity in the motor. I put it all back together and when I woke up thus am, I found the whole unit loud, to the point it was a PITA. It is fine if I remove its cover so it's rattling I'm hearing. Did the Vaseline trick, ensured it was levelled properly, and I even slid the whole unit down towards the corner of the tank. It's better but not the same. What caused this? I should have left well enough alone as it wasn't a critical clean. I don't care if I buy another 70 or maybe just the motor replacement may be the way to go.taking it back will be a tough fight, as I do have the receipt but how do I present my argument.
Thanks for any comments.