Apple iMac G5, 20-inch - Manual (Page 47)

iMac G5 (20-inch) Take Apart - Fans, Upper
5. Lift the fan out of the computer.
6. If you are replacing the fan, remove the screws from the fan grommets. Using a
screwdriver, push the fan screws out of the grommets and set them aside. Use these
screws on the replacement fan.
7. Go on to the next step to remove the second fan.
8. Depending on the type of screws present (Torx 8 or Phillips #2), loosen the two fan
screws. Note: You don’t have to remove the screws from the rubber grommets to
remove the fan, just loosen the screws.