Computer makes a whirring sound

dbuk2000

Honorable
Dec 26, 2013
36
0
10,530
Hi

My computer makes a whirring sound after keeping it on for a while. If i restart computer it goes away. Also if I turn it on its side and then turn it upright again it also goes away. Does anyone have any ideas of the potential causes

Thanks
 

dbuk2000

Honorable
Dec 26, 2013
36
0
10,530
Hi

I have opened case and seen that it is due to the PSU fan slowing down a lot to point I can practically see the blades spinning and its a very rigin spinning. This is what is causing the loud whirring noise.

But what I dont understand is why it is spinning fine initially then only after a couple of hours does this issue occur and why does it go away if I turn the PC case onto its side? any ideas?