Water cooling making buzzing noise

[Qwyc]

I have a water cooling system in my pc and everytime I turn my pc on it makes this buzzing noise. But after I run pc for a few minutes and shut it down, when I turn it back it seems to work normally. Any ideas?

 

[Lylat1an]

How is your loop configured? It may be air bubbles.

 

[Qwyc]

The sound is coming from the fan, the part where the water is cooled