Hi Hoover1979，
Welcome to the Microsoft Community!
According to your description, would like to ascertain some information with you:
You perform ANY scan on Defender my CPU is pushing 90 degrees, Have you tried any of the following three scanning methods?
- have you had this situation before?
- Any recent updates to the system?
Can you provide the full version number?
3.Your CPU temperature can be as high as 90°C when scanning through Defender and all threads are pulled full. You are describing that Defender rarely completes any scans, and that it has done so before, correct? I hope you can provide more information so that I can provide some ideas on how to solve the problem.
If what you’re trying is to use Full scan , you can try selecting fast scan to try and check if that solves the problem。
If my understanding is wrong, please point it out so that I can assist you better.
There are other users also encountered this problem, you can refer to their answers, may be some inspiration for you!
please click here:
CPU at 100% Usage when using Full Scan in Windows Defender – Microsoft Community
You can try updating Defender and check if that solves the problem.
please click here:
Microsoft Defender update for Windows operating system installation images – Microsoft Support
If the above thoughts do not solve your problem. I have analyzed, when you use Defender for security scanning, your computer temperature will surely rise, but you USE a Corsair iCUE H115i RGB Pro XT AIO cooler, the cooling effect is very good, So you can troubleshoot the hardware related to heat dissipation.
I hope the above information can help you. If my understanding is wrong, please point it out so that I can assist you better.
Best regards,
Lyla Liu | Microsoft community support expert from MSFT
The issue is recent. It only started after the 23H2 update of Windows 11 Home. I tried a quick scan and a custom scan (for scanning the entire C: drive) I haven’t performed a full scan as it would take several days and nights, as I have well over 20Tb of files on multiple internal/external HDDs/SSDs. When I convert my Blu-Rays to smaller files for my smartphone (compressing 18-25Gb 1080p to 4Gb 1080p via H.264 encoding max compression efficiency), Handbrake pushes all cores/threads to constant 100% for 2-3 hours, and it never goes above 78 degrees, 5 minutes of scanning with Defender now and the CPU gets to 88-89 degrees. When I do any scan I need to keep the Defender window open and maximized, and not use any other programs, or the scanning will stall and never recover. This is also something that started after the 23H2 update and affects all types of scans, including quick scans.
My Windows full version number is 23H2 (OS Build 22631.3007).