Mid-2011 iMac Randomly restarts within 10 min of booting up

I seem to be having an odd problem with my Mid-2011 iMac quad core i5 which I can not seem to isolate and fix. When the machine has been sitting off for an hour or more, I can boot it log in and start working. Usually within 10 minutes (regardless of what I'm doing), it will restart on its own. Upon restarting, it might get back to the login, but then restarts again, and again.. eventually I have to hold the power button down to shut it off.

I've tried resetting the SMC / PRAM, booting with just the original RAM, and using different power cords on different outlets -- all seem to get the same result.

I have replaced:

1. The graphics card
2. The logic board
3. The Power Supply

Both the logic board and power supply were purchased used off eBay and while the descriptions both said they were pulled from working units, I have no way of being 100% certain these aren't flawed.

Regardless, I wanted to put this out there and see if it was a familiar pattern to anyone. The one thing I have NOT tried is booting in Recovery Mode but was planning on making that my next step.

Is there any place I should be looking for errors? Any way to further isolate the problem? I am at the verge of throwing in the towel but this was such a solid machine up until about 6 months ago and I would like to try to salvage it if I can.

Thanks.

Did you try Safe Mode yet?

https://support.apple.com/en-us/HT201262

What operating system is on the machine?

Do you still hav e the original OS X.6 Snow Leopard discs that came with the machine when new?

ferrarr said:

Did you try Safe Mode yet?

https://support.apple.com/en-us/HT201262

Click to expand...

Ah, that's right - that was the other one I still need to try. Is there anything that can be ruled out If it no longer exhibits the problem in Safe Mode?
If the problem still exists in Safe Mode, what would be my next steps?

Thanks ferrarr

harryb2448 said:

What operating system is on the machine?

Do you still have the original OS X.6 Snow Leopard discs that came with the machine when new?

Click to expand...

It's currently running the last update to Yosemite (10.10.5?) and had been for about 2 years before it started acting up. I am uncertain if I have original discs - this machine was purchased from Apple as a refurb in September of 2012, was originally spec'd with 10.7 Lion, and to my surprise had already been updated to 10.8 Mtn Lion out of the box -- would it have come with a disc?

j3sse said:

I am uncertain if I have original discs - this machine was purchased from Apple as a refurb in September of 2012, was originally spec'd with 10.7 Lion, and to my surprise had already been updated to 10.8 Mtn Lion out of the box -- would it have come with a disc?

Click to expand...

Mid-2011 iMac's originally came with OS 10.6 Snow Leopard...and these computers would have come with a gray model specific DVD that the computer could be booted from. If this refurbished mid-2011 iMac came with 10.8 out of the box...it's most likely because Apple likes to sell computers with the latest OS on them. Apple probably updated the OS to what was the most current then (10.8)...and very likely did not include the 10.6 disks.

- Nick

As far as the problems this computer is having:

- Great idea with the SMC Reset.
- Great idea with the PRAM Reset.
- Great idea swapping out the RAM.
- Probably wasn't the best idea right away jumping into replacing the logic board, power supply, and graphics card.

After trying the "easy stuff" (like the SMC & PRAM Resets & swapping out the RAM)...the next step would have been to properly figure out if you have a hardware or software issue. And the easy way to do this is boot the computer with a 2nd device...ideally with a fresh OS install on it (such as an external HD). If you were to boot the computer from this 2nd device...and the issue disappears...then you would know that you have an OS or software issue...making all of the hard work & expense of replacing the logic board, video card, and power supply unnecessary.

Of course if the issue remained after booting from this 2nd device...then that would most likely indicate a hardware issue. And then you would pursue further troubleshooting down this path.

- Nick

pigoo3 said:

As far as the problems this computer is having:

- Great idea with the SMC Reset.
- Great idea with the PRAM Reset.
- Great idea swapping out the RAM.
- Probably wasn't the best idea right away jumping into replacing the logic board, power supply, and graphics card.

- Nick

Click to expand...

Ah, well the graphics card had been replaced a few months prior to the restarting issue arising to address an "artifacting" issue that it was succumbing to, but I thought it was worth mentioning. But yes, you are SO right about jumping the gun in swapping out the PSU and especially the logic board -- considering the time spent, and that the problem is still present, I just sunk $120 somewhere I didn't need to. Well, chalk that up to 'live and learn'.

Here is my follow-up to your advice: Six or so months ago, I used Diskmaker X to make a Mtn. Lion installer for my son's MacBook Pro, making it easier for us to do fresh installs. Considering the short 10-minute window it usually takes for the problem to surface, if this occurs while using the installer as a boot disk does it make the hardware problem seem more likely?

j3sse said:

...if this occurs while using the installer as a boot disk does it make the hardware problem seem more likely?

Click to expand...

Probably...since you're very likely bypassing anything that could be a software/OS issue on the iMac's internal drive. I guess for me I would feel more comfortable using an external HD with a fresh install of the OS on it. This better mimics real world operation compared to a boot disk...but probably is the same.

If you're experiencing these sudden restarts within 10 minutes (many times)...then that sounds to me to be "kernel panics". Many times these are caused by a hardware issue (but sometimes software)...and when it's a hardware issue...many times it's the RAM.

I know you mentioned using the original RAM (don't know if this means you had "upgrade RAM" installed before trying the "original RAM"). This is a great way to test if the "upgrade RAM" is bad...assuming the original RAM has no issue's.

In this case since you already swapped out the logic board & video card...and assuming both of these are good...then this would point even more strongly that the issue is either bad RAM...or a software/OS issue...since there's really nothing else left to test! Lol

If it is bad RAM or a software/OS issue...then your original power supply & logic board may be fine.

If you think that your original RAM is ok...try testing with the original RAM again...but only use one RAM stick at a time to test with. And...make sure you boot from a 2nd device to test if it could be a software/OS issue.

Good luck,

- Nick

pigoo3 said:

If you think that your original RAM is ok...try testing with the original RAM again...but only use one RAM stick at a time to test with. And...make sure you boot from a 2nd device to test if it could be a software/OS issue.

Click to expand...

Will do, thanks for the solid advice and quick response. I'll follow up once I have more information.

j3sse said:

Ah, that's right - that was the other one I still need to try. Is there anything that can be ruled out If it no longer exhibits the problem in Safe Mode?
If the problem still exists in Safe Mode, what would be my next steps?

Thanks ferrarr

Click to expand...

The only thing I would try is, if it does start up, allow it to stay booted for a couple of days in a row, as I never shut down any computers, unless to take them apart, move them, or rearrange how they are set up on the desk.

was originally spec'd with 10.7 Lion, and to my surprise had already been updated to 10.8 Mtn Lion out of the box — would it have come with a disc?

Click to expand...

The mid-2011 iMacs normally didn't come with Snow Leopard install disks (I have and use one) and if it was a refurb with 10.8.x, I would really doubt that any install disk would have been included.




- Patrick
======

The mid-2011 iMacs normally didn't come with Snow Leopard install disks

Click to expand...

Not true. If you purchased a mid 2011 iMac new from Apple it came with Snow Leopard install disks for version 10.6.6. I know, because I purchased a brand new mid 2011 iMac from my local Apple store and it came with two DVDs. Apple had already installed 10.6.6 on it which I later updated to 10.6.8.

chscag said:

Not true. If you purchased a mid 2011 iMac new from Apple it came with Snow Leopard install disks for version 10.6.6. I know, because I purchased a brand new mid 2011 iMac from my local Apple store and it came with two DVDs. Apple had already installed 10.6.6 on it which I later updated to 10.6.8.

Click to expand...

Not true, and I know because my mid-2011 27" iMac was purchased just after OS X Lion 10.5 was released that was installed and no sign of any Snow Leopard 10.6.6or7 disks.

Maybe that's the way Apple did it in Canada.

When I called Apple, the techs weren't even sure the iMac could actually run SL and sent me the special SL install disks at no charge. I also had to explain that their ads said it could and was one of the main reasons I bought it being the last Mac model to be able to do so.

PS: I think this is repeating some earlier discussions on exactly the same topic.




- Patrick
======

Not true, and I know because my mid-2011 27" iMac was purchased just after OS X Lion 10.5 was released that was installed and no sign of any Snow Leopard 10.6.6or7 disks.

Click to expand...

I guess it depends on "when" you purchased a Mid 2011 iMac. Those models were being sold well into 2012. However, as I explained above mine came with two Snow Leopard DVDs - version 10.6.6. Any blanket statement with regard to what that model came with will have to have an asterisk. ;D

chscag said:

I guess it depends on "when" you purchased a Mid 2011 iMac. Those models were being sold well into 2012. However, as I explained above mine came with two Snow Leopard DVDs - version 10.6.6. Any blanket statement with regard to what that model came with will have to have an asterisk. ;D

Click to expand...

Yep, it's the same in "the states" mine was purchased as a refurb in 2012 and came pre-loaded with 10.8 - so nope to the SL discs -- but that has never really been an issue since creating the flash-drive install. I will be testing out all possible methods tonight.

A couple of things to try;

First is Onyx, https://www.titanium-software.fr/en/onyx.html, download the version for your macOS version. Install it and then run the Automation setup, without changing anything, except maybe the Permissions option.
Second is EtreCheck, https://etrecheck.com, run it and post results here.

Never got that far. I'm wondering if it's heat-related. If it's sat for awhile, it will boot up fine and go for 5-7 minutes, after that it restarts.

The first restart will usually get it back to the login screen, then it will restart again.

The second time it may go partway into loading up and then it restarts until the cycles become closer and closer together until it's just in constant reboot. At that point it doesn't matter if i'm holding down keys to boot from recovery mode, safe mode, install disc... all respond in the same way.

That's why I think it's heat. Something (I don't know what) starts off 'cold' and the machine works... as it's running and that thing heats up, it causes a reboot. The more it reboots the warmer it gets until it's in the reboot loop. What could that thing be, though?

I should also note that this is with any of the ram sticks individually installed.

I suspect you're probably going to have to open up that machine and check to see what's going on inside. Your iMac has three fans (newer models only have one): CPU, HDD, Optical Drive. If any of those fans stop or the temperature sensors for them are defective, the machine might overheat.

Go to www.ifixit.com and find out how to take your iMac apart. Since yours is a 2011 model, it's held together by magnetic strips and can easily be opened with the proper tools. The ifixit site also sells the glass sucker and spudgers.