With all due respect it's not the pump. The power draw is the same as it was when new. The rpms are the same as new and there is no noise. I can use a stethoscope and hear the pump running. It's nice and smooth with no air bubbles going through it. I think the coolant used is supper freaking cheap and not to spec. Thus it's breaking down and clogging the block micro fins, insulating the cpu from the water path. I've seen examples of this on the net concering Corsairs liq. coolers. I have also seen it in my professional life.Sounds like the pump is going bad .. progressively moving less coolant resulting in progressively higher CPU temps. I'm assuming the radiator is clean.
I work for a manufactures rep that deals with this stuff. We rep Xylem Company's like Bell & Gossett a massive pump manufacture. Xylem bought Lang and we use a lot of the Lang's in Radiant Heating, Solar Panels and other applications. I work with heat exchangers at a massive level. Again Bell & Gossett, Standard Co., Sentry, Heat exchangers in boiler and chillers. And rep a cooling tower line. And work with many others. We also rep Dow Fluids used in these systems that are safe for humans at the food grade level.
I think Corsair has used a very cheap coolant mixture in there coolers. Over time it separates and breaks down. Sometimes very quickly. And leaves a gelatin type martial stuck in the wrong places. Almost all people that have broken down a AIO notice a very fowl smell from the fluid. This is because the additive used is organic. Good cooling / heat / protective additives will have no smell. Or at worse smell like auto antifreeze.
Anyway proper parts are on order. I want this junk H100i gone. I knew better than to buy this junk!