Yeah, most definitely air churning. As long as you keep working large bubbles out and keep replacing the air with water, you will be fine. Make sure you work the air bubbles out of your radiators; this is where you'll encounter the biggest issues with air in your system.
Yea, i have the same problem with this pump (which is what brought me here).. It's not like a dark, fan-like sound, but rather a high-frequenzy REALLY annoying sound coming from the pump. I DO NOT have any air bubbles, at all, and even though the pump/reservoar is not 100% full, there is no air coming into the pump. Its really just the engine making a frustrating noise.. I'd rather listen to the reference GPU fan than this I have a fan controller, which on i set the radiator fans to max, and THEN i barely hear the pump <3. But those fans are loud too, so: is there a way to kinda "isolate" using rubber or something, to fix this? A friend has the same pump/res (wc kit) and has the same sound..
Does the noise get better? Is this usual? Can it be fixed?