So I bought a new (used) GPU and a new case. I plugged everything and everything works fine, but sometimes, randomly, a bbbrrrrrrr noise starts coming out of the case. I tried unplugging my fans and it kept coming back. I checked if its the GPU and still doesn't seep to be it. Can someone help me out? Also no its not coil whine.
Check each and every fan for debris, dust, cables or any other thing that may obstruct them from spinning free.
It can also be a fan bearing going bad so it wobbles a bit, or it can be coil whine from the PSU. Many options actually, you have to find first the source and then we can troubleshoot.