I have a masterflex 7523-60 that makes a squeaking noise just like a brush motor, and it's brushless. I have one running now that has brushes that sounds like an air pump, not bad though. I actually just turned on the 7523-60, and it's quiet. I know in a few weeks the squeak will be back. If it was in a fish room, basement, or under a stand you may not be able to hear it. Maybe I need to just look into a repair shop local. These masterflex pumps are so dependable running non stop same ml/min month after month. If I had to use another mj1200, or tee of main return for feed pump I would just buy a doser for 2 part.