Computer makes a whirring sound

[dbuk2000]

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

 

[Nuclear101]

Try to see if any case fans are rattling against the side of the case. Some types of fans don't work on one position.

 

[dbuk2000]

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?