iMac Fan Randomly Becomes Loud

Over the past few months I have realized with my iMac that the fan becomes very loud and finally slows down after 10 seconds of irregular spinning.

Recently it did this so I decided to manually shut down my computer. When starting up the next morning it froze, it also didn't sound off the Apple Gong. My first start-up attempt resulted in my Mac freezing at the point where the Apple symbol appears with a grey background and the circular loading symbol. I restarted my computer manually and tried again. Again the Gong did not sound off but did start-up.

Any help would be greatly appreciated, answer respectfully or not at all. Thank you.

It sounds like a hardware problem of some sort. The loud sounding fan and then a system freeze could be related to logic board problems. Is your iMac covered by Apple care? If it is, make an appointment with the genius bar and have them check it out.

If it's not covered by Apple care, try starting the machine with your install DVD. Then run the Apple Hardware Test. See the following LINK.