Whenever I turn on my PC, the power supply fan makes a loud grinding or rattling sound for about five minutes. It gradually becomes quieter, but I can still hear a faint grinding for another few minutes before it eventually stops. The PSU was obtained secondhand several years ago and has only been used for around six months. Is the fan bearing failing, how long might the power supply continue working, and what could happen if I keep using it? I cannot afford a replacement immediately.
2 Answers
If the unit has any warranty, arrange a replacement or repair instead of opening it yourself. Since this was a free secondhand PSU with an unknown age and history, I wouldn’t rely on it for important hardware. A failing fan could eventually stop completely, causing the PSU to overheat and shut down, and a defective power supply can potentially damage other components. Avoid heavy use if possible and replace it as soon as you can.
That sounds like a failing fan bearing. The noise changing as the PSU warms up is a common symptom. There usually isn’t a safe user-level repair, and opening a power supply is dangerous because it can retain a high-voltage charge even after being unplugged. The safest solution is to replace the PSU, or have it serviced by a qualified technician.
How long could it keep working, and what is the worst-case scenario if I have to keep using it temporarily? I can’t afford a replacement right now.

It came from someone locally several years ago, so there probably isn’t any warranty available. I’ll avoid opening it and start looking for a replacement.