iMac's kernel task causing high CPU load, hindering macOS update

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iMac's kernel task causing high CPU load, hindering macOS update

2019 27-inch 5K iMac with 6-core intel i5 & Radeon Pro 580X. Currently on Sonoma 14.4.1. Nothing but Activity Monitor is going, CPU temperature stays around 70 degrees C, kernel_task takes up 350-400% CPU constantly. I've reset SMC, NVRAM, booted in safe mode, unplugged all accessories, restarted multiple times, blown air around the fan ports, the issue persists. Occasionally after a reboot everything works fine for two or three minutes, then at one moment kernel_task takes over.

I'm trying to update to Sequoia 15.3, hoping that fixes whatever bug is still causing this. It downloaded the update, but is stuck on "preparing macOS Sequoia 15.3.... 30 minutes remaining." It's been about 6 hours with no progress.

I've read that a possible problem is that there's just too much dust in the machine. That's possible, it is in a dusty area. But the problem was not a gradual rise in inefficiency, it was functioning perfectly well under high-stress video editing programs yesterday, and not functioning today.

Any ideas?

[Re-Titled by Moderator]

iMac 27″, macOS 14.4

Posted on Jan 30, 2025 4:12 PM

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Answer 1

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rkaufmann87

Level 10

148,682 points

Jan 30, 2025 10:56 PM in response to WentzvilleCC

I suspect the HD on your Fusion Drive may be failing. So, before you do ANYTHING please backup the computer and ensure the backup is working correctly. Once you have done that please download DriveDX and test the Hard Disk. Open the report and if it shows ANY errors that means the drive is failing!

Considering the computer is about 6 years old that is a distinct possibility. It is also possible the HD has become unfused.

When you run Drive DX, you want the report on the HD not the Fusion Drive and not the SSD portion of the Fusion Drive.

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Answer 2

rkaufmann87

Level 10

148,682 points

Jan 30, 2025 4:22 PM in response to WentzvilleCC

We will need you to post an EtreCheck report of your system so can look for obvious issues. Without any report, we are really blind and can only guess.

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Answer 3

rkaufmann87

Level 10

148,682 points

Mar 14, 2025 1:28 PM in response to WentzvilleCC

Yes, you can transfer to an external SSD and use that as your boot drive. Here are detailed instructions on how to do that:

How to setup an external SSD as your startup disk

The external SSD I'd recommend is the https://eshop.macsales.com/item/OWC/TB3ENVPFX02/ due to it's extreme high quality, thoroughly tested and made for Macs, reasonable cost, speed of the drive and the vendor is excellent.

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Answer 4

John Galt

Level 10

157,260 points

Jan 30, 2025 4:51 PM in response to WentzvilleCC

Please determine if the same problems occur in "Safe Mode": Start up your Mac in safe mode - Apple Support. An EtreCheck report would also be most helpful.

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Answer 5

WentzvilleCC Author

Level 1

4 points

Jan 30, 2025 7:03 PM in response to WentzvilleCC

EtreCheck Report

EtreCheck Report:

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Answer 6

rkaufmann87

Level 10

148,682 points

Mar 13, 2025 5:20 PM in response to WentzvilleCC

I still suspect the HD portion of the Fusion Drive.

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Answer 7

WentzvilleCC Author

Level 1

4 points

Mar 14, 2025 12:14 PM in response to rkaufmann87

Understood. I know replacing the drive isn't really an option without shipping it off to Apple, is it possible to save the computer by transferring everything to an external SSD and running everything off of that?

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