My iMac fan is super loud! What do I do? Is it going to overheat or something? Please help. Thank you!

try it:

SMC reset      https://support.apple.com/en-us/HT201295

Zap pram   https://support.apple.com/en-us/HT204063

Please post a fresh Etrecheck report and we can look for more issues. If nothing shows up please do 3 - 4 SMC resets with no wired peripherals (printers, scanners, cameras, etc...) and then retest.

SMC Reset

I doubt it's a design issue because we would have had more than just your report of the issue.

Download and run Etrecheck. Etrecheck is a diagnostic tool that was developed by one of the most respected users here in the ASC and recommended by Apple Support  to provide a snapshot of the system and help identify the more obvious culprits that can adversely affect a Mac's performance.

IMPORTANT:

Before running Etrecheck assign Full Disk Access to Etrecheck in the Etrecheck's Privacy preference pane so that it can get additional information from the Console and log files for the report:

Also click and read the About info to further permit full disk access.

Copy the report

and use the Additional Text button to include the report in your reply.

Then we can examine the report and see if we can determine what might be causing the problem.

The best antivirus, cleaning app, and overall maintenance app for Mac OS is Mac OS itself. All you need to do with Mac OS to keep it secure and running well is to keep it up-to-date and do periodic (about 1x per week) restarts. Other than that, leave it alone. Adding third party antivirus, cleaning, security and other types of maintenance apps to Mac OS adds no additional level of security. The only thing these apps do is have the opposite affect users want. They make Mac OS slow, unstable, generate odd behavior (much like you are experiencing) and make Mac OS appear buggy. 

Please locate the developers uninstall instructions for CleanMyMac and follow to the letter. Then restart in Safe Mode per the directions in Use safe mode to isolate issues with your Mac and then restart normally. 

Do you have the iMac situated so that you have to tilt it down while you're working with it? Several users did and had fan issues. Tilting the iMac up and getting the air vents away from the stand solved their problem.

The report is clean. It appears it's time to make an Apple Genius Bar or Authorized Apple Service Provider appointment for a free (at Apple) diagnostic check.

Be sure to have a full and current backup of your hard drive before taking it in.

By the way, it often takes several SMC resets for it to finally work. So if you don't have luck the first time please do it 2-3 more until it does.

This appears to be an issue Apple doesn't want to deal with. I've had fans running at 3800+ at random times when not under load and cool room temperatures. Apple Diagnostics gives codes PPF004 and PPF003. I took the iMac into the Apple Store "Genius Bar" and after a week had me pick up the computer stating they could not reproduce the fan issue. That's it. Come get your computer, there isn't a problem. Everything's fine for a few days and now the fan is starting to act up again. Apple used to be a reliable company. Now it seems everything is politics and CYA.

I uninstalled CleanMyMac and within a few hours the fan started acting up again. It's acting even more erratic than before. Not happy with Apple these days - I'll just live with it and hope something major doesn't happen in the middle of a project deadline.

Hi - I did 4 SMC resets in a row and ran another EtreCheck. Report is in Additional Text.

First times the fans were running fast starting this morning were approx.: 7:09 AM, 9:20 AM and 9:28 AM continuing off and on throughout the morning. Fan speeds in excess of 3900 RPM at 90 degrees F with room ambient temp. approx. 68

I might have posted this to the wrong discussion - here it is again if I did:

Fans began running fast as soon as I woke the computer this morning at approx. 7:09, 9:20, 9:28 and continued off and on throughout the morning. Fan speeds 3900+ at 90 degrees F and ambient room temp. approx. 68 degrees F

I wouldn't even be using in iMac if they hadn't doubled the cost of a MacPro tower. We graphics professionals rely on them but the cost increase put the machines out of range for a good many of us.

I'll try tilting it up a little but that shouldn't be an issue there's 3" of clearance. Thanks for the input. It has to be a design issue.