My 2x 980TI Hybrid "recently" developed a buzzing that's coming from the top mounted radiators. I stopped all fans and this noise continued. It appears that the sound was previously masked by the rather loud stock radiator fans compared to my new Corsair SP120 Quiet Edition fans. It's made my quiet build not so quiet and is pretty frustrating for cards that I spent $1500 on. 
 
www.youtube.com/watch?v=nyIIvRDsuqQ&feature=youtu.be 
 
Attached is also a photo of my case showing the top mounted radiators. 
Is there anyway to fix this without having to go through a full RMA process?
 
Thanks much, 
 

a
Its probably the pump making the fins rattle somewhere on one of the rads, if its not the pump itself making the noise. If you can figure out where its coming from you can use a drop of hot melt glue on that spot to stiffen the vibration on the fins. The only other thing would be maybe some screws somewhere have backed off a little over time and now your hearing it before theres a big failure....like a warning! Check all those screws thoroughly and see what you can find, it may be worth it to you in the end to stop a catastrophe.