I just bought used Evga GTX 1080 FE which had hybrid kit installed. Radiator on this keeps humming noise when it has direct contact to any surface (floor, installed in pc case etc) , noise disappears when I hold the rad in my hand, but i can feel vibration. Humming noise reduces when I put to fractal venturi HP-12 fans on push-pull config, when rad isnt getting so much direct contact to the case, bu its still there. I never had any AIO systems before, so I dont know if this is normal behavior, or is my unit somehat faulty? 

Could be air bubbles working through system - Did you follow tipping directions to get trapped air out?
 
Or Fan vibration
 
You could use isolation mounts to stop harmonics.

For the first question, I did.
 
Its not fan vibrating, cause humming exists with fan unplugged.
 
Fractal venturi fans have huge fully rubberised corners which act as isolation mounts themself pretty much.
 
 

So, you think pump is surging or pulsing ?
 
Use long solid object (unless you happen to have a stethoscope) like a screw driver --- listen to the pump and or radiator
 
Be very careful not to touch anything with power to it like the MB
 
Wooden dowel may work as well, and is not conductive

Cool GTX
So, you think pump is surging or pulsing ?

 
Yeah, I think it initially comes from the pump, and then it tranfers to the rad. 
 
Do you mean "listen to the pump" as through the hybrid kit's shroud, or shroud removed and directly from the pump?

Partsi

Cool GTX
So, you think pump is surging or pulsing ?

 
Yeah, I think it initially comes from the pump, and then it tranfers to the rad. 
 
Do you mean "listen to the pump" as through the hybrid kit's shroud, or shroud removed and directly from the pump?

 
Shroud is OK
 
Also Radiator solid end, where hose attaches
 
Should be a steady sound

It's vibration between the rad and case, makes sense. If it bothers you, try some thin rubber washers between the case and rad.

That should stop it.

This rubber washers between the rad and case will fix it. It's vibrating on the case most likely.

3etatester
It's vibration between the rad and case, makes sense. If it bothers you, try some thin rubber washers between the case and rad.

That should stop it.

+1

https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcTd9LgAF7pOM2otrB7JJv5ec74QV6mQX1fWNAIzknd7BsruWWHd

I use these fractal fans in push pull on the rad, those rubber corners should work better against vibrations than rubber washers.

But still that humming is pretty loud, equal to two 7200rpm HDD:s vibrating against the case. I think that those screws are still transfering that humming to the case.

Also I can feel vibration through whole GPU-shroud, especially on top where the pump is. Even when I stop radial fan with other hand.

Its not huge deal when GPU is under load, but when on light desktop usage its very annoying.

Sorry for my english, writing from Finland. :D