2008 iMac 24" fan problem. anyone have any suggestions?

so as the title states, 2008 iMac 24" 2.8 Intel Core 2, updated to latest os and update

So the computer has been bulletproof since the day I got it in 2008, but all of a sudden the fan has started going at full speed, very loud, I have never heard them spin so hard, after about 10 minutes of turning it on. I took it to the apple store and they told me since my iMac is "antique" (he actually used those words) that there's nothing they can do for it, and maybe a third party can fix it. So basically Apple can't fix my Apple. They also suggested reinstalling OSX as the cause my just be software related. The thing is that even if i boot to the bios using the option button the fan still starts blaring, making me think its not software but hardware related. Also the computer feels cool to the touch, not hot at all. Anyone have any suggestions on what I can do to take car of this issue.