2011 27" iMac keeps crashing and restarting

interesting thread. My 2011 27"iMac is playing up too. Keeps crashing and restarting, gets grey screen with pink stripes. I have restarted on restore disk several times, reinstalled the OS several times, but to no avail. Hardware test said all was fine!
Should try a complete clean install of OS or is the HDD failing?

Any news on this thread? Did anything work? I may have the same problem.
My 2011 27"iMac is playing up too. Keeps crashing and restarting, gets grey screen with pink stripes. I have restarted on restore disk several times, reinstalled the OS several times, but to no avail. Hardware test said all was fine!
Should try a complete clean install of OS or is the HDD failing?

Are you saying it boots and runs from the restore disk, and is that the SL 10.6.x DVD disk or from the Recovery HD "disk" volume?

Sounds like a hardware problem. Restart your 2011 iMac in Safe Mode and let it run that way for awhile to see if it crashes and does the same thing. And, if it's going into panic include the panic report with your next reply. Be sure to look in your logs for any other clues as to what's happening.

it wont restart in safe mode either now

@Yass John:

Do not start another thread on the same subject and do not tag your post on to another thread. You can understand the confusion this causes when trying to answer your posts.

I created a separate thread for you and merged your posts together here. Let's keep it all in one place. Thanks.

Yass John said:

it wont restart in safe mode either now

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It could be a hard drive problem, but the symptoms you described above do not sound good with respect to the graphics. Is there an Apple store close to you? The genius bar will run diagnostics for free and give you some idea of repairs.

sorry, but what is the genius bar?

The genius bar is the quick maintenance and diagnosis counter at all Apple Stores. It's maintained by trained Apple technicians. If the machine needs repairs, the genius bar will tag it and send it off for repairs. Most repairs like swapping out a hard drive are usually done right in the store's repair division. Major repairs are sent out to the closest Apple repair depot.

Yass John said:

interesting thread. My 2011 27"iMac is playing up too. Keeps crashing and restarting, gets grey screen with pink stripes. I have restarted on restore disk several times, reinstalled the OS several times, but to no avail. Hardware test said all was fine!
Should try a complete clean install of OS or is the HDD failing?

Click to expand...

These are common symptoms of a failing video card. Apple has a specific test to confirm this that can be run by Apple or an AASP.

Thank you. Does the Hardware Test check the video card? if not, can I test it myself from Apple online?

The Apple Hardware Test is not very good at spotting a defective graphics card or even a hard drive for that matter. And no, you can not test it online. As I stated above and also as Steve advised, take it to Apple for testing. Is there an Apple store nearby?

Yes, I think it has come to this now. Unfortunately, the nearest Apple store is about an hour away. We do have a Apple licensed computer store in town. I will wander down on Monday and ask them what they can do, what level of testing.
Thanks for your help/suggestion
John.

Keep in mind that an authorized Apple repair service will charge you for the diagnostics. An Apple store will run the diagnostics for free. So if you're willing to pay for whatever their minimum diagnostic fee is, take it on in to them.

Yes, I understand. That is why I do as many tests myself, Restore disk, hardware test etc. But I think now that I have exhausted my home options except a clean re instal of Yosemite. It seems from responses here, that that may be a waste of time and the iMac may crash before it is completed. Then I would be stuffed!

chscag said:

Keep in mind that an authorized Apple repair service will charge you for the diagnostics. An Apple store will run the diagnostics for free. So if you're willing to pay for whatever their minimum diagnostic fee is, take it on in to them.

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That may be so in the U.S., but up here in Canada any such charges seem to depend on the policy of the company and often no charge for a diagnosis, if the user actually even lives in Canada.

Yass John said:

Thank you. Does the Hardware Test check the video card? if not, can I test it myself from Apple online?

Click to expand...

No, it won't. The VST is an option within Apple's diagnostics that boot from a netboot server at an AASP or an ARS. Unless also an AASP a reseller won't have the ability to test.

pm-r said:

That may be so in the U.S., but up here in Canada any such charges seem to depend on the policy of the company and often no charge for a diagnosis, if the user actually even lives in Canada.

Click to expand...

LOL, the policy of any company is to make money. Doesn't matter, Canada or US. There are those service outlets who will deduct the diagnosis fee from your repair bill if you should decide to get it repaired there. I was in the private electronic repair business as a sideline to my government job and our minimum fee applied as soon as you brought whatever into our shop to have it repaired, or requested an estimate of repairs.