The fan should not be loud. It sounds like the fan has become un-lubricated.
The same thing happens to Power Macintosh 6500 CPU fans, and the really small fans on certain ATI Video Cards in G4 towers. We wasted a ton of money trying to figure this out on our 6500. This one shop sold us on a new power supply for $200 and it stopped for a few months and then started again. (Now I know we were probably ripped off and they just put WD-40 on the CPU fan). Another shop finally figured out it was the tiny little CPU fan and installed a new one.
A year later it started up again so I just lubricated it myself.
Anyway... lubricate the eMac fan, and I bet it will improve significantly.
The same thing happens to Power Macintosh 6500 CPU fans, and the really small fans on certain ATI Video Cards in G4 towers. We wasted a ton of money trying to figure this out on our 6500. This one shop sold us on a new power supply for $200 and it stopped for a few months and then started again. (Now I know we were probably ripped off and they just put WD-40 on the CPU fan). Another shop finally figured out it was the tiny little CPU fan and installed a new one.
A year later it started up again so I just lubricated it myself.
Anyway... lubricate the eMac fan, and I bet it will improve significantly.