Fan Noise and Freeze with Mac OS 10.5.7

I have a Power PC G5 1.8 GHz Dual processor running OS 10.5.7. I have been having intermittent system freezes with a very loud fan noise. It doesn't seem to coincide with any software or activity, but usually happens when I leave the computer alone. Maybe it misses me... ha. I have been having some other unrelated software issues for some time (had kept updating over very old stuff, leaving old things around, classic still resided but unused, etc.) so decided to completely erase the hard drive and reinstall the system software, hoping that the main problem would be resolved. Took a break from set up and got the same freeze and jet loud fan noise. I currently have only the system software and kensington mouseworks installed. I've been searching online but haven't found any specifics. Can anyone shed some light?

ok first off you want to find out which fan is noisy, the power supply or CPU fan. either of the fans will cause a problem. if it is the cpu fan just replace it, if it is the power supply fan replace the power supply. to identify the fan it might be best to leave the side off. once you have done this give me an update.

Well, it sure sounds like it's all of them. I'll need to wait until it does it again to find that out and there's nothing I can do that actually forces the issue. I'll post again whenever it happens. Do you think it's a fan/hardware issue or is it a system software issue (don't know which comes first, the fans or the freeze)?

It's probably a hardware issue. The fan noise could be caused by bad bearings which would cause the fan to wobble, make noise, and slow down. That in turn raises the heat level causing the machine to freeze.

As you've been advised it could either be the CPU fan or power supply fan. My guess is it's the power supply fan.

Regards.

yes i agree with chscag. when i have an issues with the fans, when they are making noise i will touch the fan to stop it for a second and if that is the problem fan it will not be making noises. many people will probably tell you this is a horrible idea but really what is any better then my way?