I have a 5 year old PC, and until now it hasn't made me any problems on the hardware side. For a few weeks, a very loud noise comes from my PC. At the beggining it was only heard in the first 10 minutes from PC start than eventually stop.
Yesterday I opened my PC case and cleaned the dust again (last clean was 2 months ago), but the noise didn't stop. I thought it might be the Power Supply as the CPU Fan wasn't doing the noise, neither did the GPU One (Chcked with SpeedFan). I've cleaned the dust in the PSU, started the PC and it was all-right, but in the next day's morning, surprise, the noise was back.
I've also noticed that hitting my PC case made the noise go away before, now when I hit my PC the noise stops, for 10 seconds than it returns.
The PSU Fan is inside the PSU, and I barely have acces to it, also I'm not sure if after removing the PSU I'd be able to mount it back, but do you think lubrifying it would fix the problem ?
The fan in the PSU most likely cannot be lubricated; it will be of the same sealed-bearing type as the other fans in your PC.
Opening a PSU can be a VERY risky proposition, with internal capacitors potentially storing a lethal charge.
Five years is not a bad lifespan for a fan. It may simply be time to replace the PSU. You will no doubt also be able to get a much more efficient one than what you have, and higher quality.
What is the brand, model, and wattage of the one you have?