I had to hard to swap motherboards (ASRock X399 Taichi failed on me) and now my 360 is noisy... like a fishtank. It sounds like someone is taking a shower in the other room or something. I had no noise from the system on the Taichi board, but have a ton of noise now. While I was swapping the motherboards, I didn't take the cooling fully apart, but I did lay the case on it's side to make it easier to work on. I wasn't concerned about air bubbles, since it's a sealed system. The only other thing I would think could cause it (besides something going bad... it's only a few weeks old) would be maybe different voltage to the point between the header on the ASRock and the one on my new board (Asus ROG STRIX X399-E Gaming). There are three different headers you can use. After reading this thread, I did what most do and plugged the pump into CPU_FAN and the radiator fans into CPU_OPT. Temps seem normal (32-32C for CPU) so far (no OC), but the bubbling is annoying. Anyone experienced this?