I have had this system for probably 4-5 years and I haven't been watching the temperatures, but the other day I was. At idle the CPU is running around 22C and the H80i around 27C (I assume that is the temperature of the water). Reported using Corsair Link 4. See my profile for info. Running stock speed. Yes, the water is hotter... at idle!
When I push the CPU with Prime95 (max heat) the CPU goes up to 90C but the water temperature (well what Corsair Link outputs) only goes up to about 34C. For tests like this I have the fan on max (about 1500rpm) and the pump on performance (about 3000rpm) just to be the best cooling.
I was confused how the water could be so COOL but the CPU so HOT! Since the water temperature changes and the fan speed and pump speed changes (using Corsair Link) I assume those are working. Well, I can clearly see the fan spinning. One tube is warmer than the other so I assume there is some water circulation. Perhaps not ideally working, but nothing obvious...
My only conclusion was that the water pump cooler wasn't mounted well on the CPU. Got some Artic MX-4 and removed and replaced it. Temps pretty much the same. When replacing the cooler I noticed some sloshing of water and was concerned, but I'm assuming (?) this is standard. The pump is quiet so I don't believe it's pumping some air or cavitating.
While perhaps not a top of the line water cooler, I'd expect it to do better than this and when I built the system I assume I had much better temps because I do remember testing it!
Any insights would be greatly appreciated!
Thanks