I'm posting this for a friend of mine. I put together a pc for him a few years ago and it included the EK XTOP Dual DDC pumps with the dual top. Around a year ago, one of them began making a clicking sound, so he decided to replace them with new pumps. Now, not even a year later, both new pumps are clicking in the same manner again. This is the first real water cooling loop I've built for someone and I really don't know what could be going wrong with the pumps. They're ran at around 40% all the time (He has 2x 480 Black ICE SR2 rads in the loop cooling his 5960x cpu and a single GTX 980, overkill I know lol.) What I'm wanting to know is what could be making the pumps fail like they are? We used premixed coolant that is fine for the loop, they weren't ran dry, the res feeds the pumps from above, and the pumps are below everything else in the entire loop. When I checked out his previous failed pump, you could see some marring where the impeller appeared to be making contact with the bowl it sits in on the pump. There was definitely a difference in how it felt to spin that impeller vs. the new ones that we received. Is it possible they may just need cleaning? His loop seems to be very clean without buildup in the coolant, so I'm kind of at a loss here and I don't want him wasting any more money if I'm doing something wrong and it's making them fail so quickly.