Mid-2011 iMac 27" running from Thumb Drive - Hard Drive may be bad...


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Jan 8, 2021
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I recently experienced a problem with my Mid-2011 iMac 27". The screen started to flicker, then would go blank. I could restart and it would work for a bit, but it wouldn't take long before it would be a problem again. The time it would function got shorter and shorter until eventually it was stuck in a boot cycle. I thought it might be my Radeon graphics card again. This failed about two or so years into ownership previously but was replaced by apple.

However, when I ran some diagnostics, it showed my hard drive fan had died. I tried a number of different things to get to my hard drive and finally had some success with booting to my Restore partition. I was able to run some utilities, which told me my hard drive was full, although it is reporting nearly 30GB free of 1TB. I have been unable to delete anything on the drive via Terminal as a result of the drive being "Locked". I have attempted a number of things including but not limited to disabling SIP, changing permissions using chmod, etc. Nothing was working, so I figured out how to get High Sierra installed on a thumb drive. I am actually typing this message on my iMac via High Sierra on a thumb drive.

So with all that said.

Is it safe to say if my computer is running perfectly fine from the thumb drive, that my Radeon graphics card is NOT to blame for the flicker and boot loop that I was experiencing, and the problem is likely my hard drive? I am thinking I may just get an upgrade kit to move the hard drive to an SSD, and swap out my current hard drive, hoping that it isn't damaged enough to not be able to get stuff off of it. I can see my drive, but when I ran the First-Aid check, it came back with an error on the original hard drive, and the was unmounted. Now it won't mount (haven't tried restarting yet). Not sure how much luck I will have getting files off of it.

What would you folks suggest as a good upgrade choice. I was thinking of an iFixit kit with a Crucial SSD. I might go smaller than the original since I have a drobo, and it makes a reinstall a little less painful going forward if I had another failure.

Has anyone had any experience cracking the iMac open. I have fixed a number of iPhones for batteries, screens, home buttons, cameras, etc. Is it similar in time and patience needed. Any tips?
Thanks in advance,


Ambassador Team Leader, Senior Moderator
Jan 8, 2012
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Hopefully those who have an iMac will respond soon. With that being said, your computer is going on 10 years old and will probably start breaking down on it in stages. If it were me, I’d start planning to get a new or newer model.