A few days ago I noticed one of my fans on my PC (the one at the edge of the case, attached to the side of the case, not the PSU/CPU/GPU fan) was running very loud, this happened for about twenty minutes after I started up the PC. Didn't happen again until yesterday morning, where i started up the PC and it did it again, then returned to normal. Later I turn the PC on again, and it continues to make this loud noise, for twenty minutes. Then it stopped for about half an hour, but then started again until I turned off the PC (about half an hour after the noise started again, so the sound didn't seem as if it was going to go away). Normally the sound gradually got quieter and slower until it stopped, but this time it wasn't. I could tell that the sound was coming from this case fan because I know where it is inside of the PC and I heard the noise being the loudest there.
The temperatures on my CPU and GPU were both normal (E8400 and GTS 250) and the same as they'd ever been. So this fan can't really be that important; but it would still need to be replaced. When I opened up the PC today to clean it, I realised that this fan was very dirty, and the PSU fan, GPU fan and CPU fan were all relatively clean (the PSU and GPU, along with their fans, were changed in an upgrade three months ago so they are very clean, and the CPU fan didn't seem very dusty).
But after I cleaned it and turned the PC on, again it performed the same as ever but that noise was still there and as bad as it was before. I know for sure its coming from that fan and that fan only. I don't think the fan could have anything blocking its way, it didn't look as if that would be possible.
So whats happened? Does the fan just need replacing? If I took the fan out, will that be bad for the PC? (the fan takes air in, not out... i think) Should I just replace the fan? Only problem with that is that I took the model number and googled it... its some cheap chinese thing that I can't buy anymore (a family friend built the PC for us). The fan screws onto the edge of the case, so could I buy another fan of the same diameter and replace that with my busted fan?
Remove the fan, if it has a sticker on the back, remove it, you should see the spindle, if not, may have a little rubber cover, pop it off and then add some light machine oil, give it spin to work oil in, don't use WD40.