the fan of my iMac runs too loud - Can you help determine why it over heats?

Click on this link to read about fans and fan noise in your Apple product --> About fans and fan noise in your Apple product - Apple Support

If the fans in your device run fast even when it isn't experiencing heavy usage and is properly ventilated, follow the steps for your device:

• On an Intel-based Mac: Reset the System Management Controller (SMC)
• On a Mac computer with Apple silicon: Close and open the lid on your laptop, or restart your computer.