Hi, I have a ~2yo Core i5 2500k with a stock fan&heatsink and a pretty old case fan. About two months my computer started making a strange rattling noise. I thought it was the HDD so I replaced it, but recently it started again, so I ruled that out. Opened the case while PC was working, and the sound seems to come from one of the fans. SpeedFan lists my PC as having two fans: one CPU and one GPU, while in actuality I only have the CPU fan and the case fan (I'm def not seeing any fans on my GPU - AMD HD 6970), and I'm not sure which is recognized as which. The rattling sound comes from the fan marked as GPU, since it changes when I change its speed.
The other problem is CPU overheating. When I run the computer normally CPU temperature can quickly go very high, even above 100°C. Even when idling it tends to be around 60°C. When I open SpeedFan, GPU fan speed is always 25-27% and CPU at 100%. When I adjust it up to 50% manually, CPU temperature only goes to 80ish max when gaming, and I can keep it even lower by upping the speed but at that point the normal fan noise becomes very loud. Rattling is more or less the same at different speeds, except at some speeds you hear a wobbling sound, like spinning a plate, which changes in speed as you change the fan speed. FWIW I've ran RealTemp too and it detects the same high temps, even though the PC seems to run perfectly normally, no slowdowns, BSODs or anything out of the ordinary. If it weren't for the rattling noise, I never would've found out about this.
I don't really care for the high temperature, all the components in my PC have been used for years and I doubt this is gonna kill them, but the noise is driving me mad Can you tell me what to replace to fix this, thanks.
For your CPU issue I think your thermal paste has dried up. Take off the heatsink, clean off the old thermal paste with isopropyl alcohol (70%+, 90%+ preferably) and a lint free material (e.g. coffee filters, lint-free cloth) then apply some fresh thermal paste and reseat the heatsink. You could also try cleaning out the heatsink itself - have you ever dusted your PC? The CPU fan could be clogged full of dust which would cause the high temps. IF all of that fails you could try getting an aftermarket cooler such as the Hyper 212 EVO.
I think you should take the side of the case off when using your PC and locate which fan is definitely causing the rattling. If it's the case fan you can just replace it. It could be as simple as an issue with the fan bearing.