Problems with partition map

Discussion in 'Mac Basics and Help' started by hardhatmac, May 6, 2016.

  1. hardhatmac macrumors regular


    Jun 13, 2006
    Hey everyone,

    I've been having problems with my 2009 27" iMac. It just started acting up, like, getting stuck on the grey screen during boot, not being able to wake up after sleep, etc.

    Here's what I've tried (in no particular order):
    Resetting the PRAM
    Resetting the SMC
    Reseating the RAM
    Removing 3rd party RAM (leaving only the stock chips)
    Removing Apple RAM (leaving only 3rd party chips)
    Replaced the HDD
    Reformatted the new HDD (multiple times)
    Treid reformatting in a difference scheme (it then forced me to use GUID to install OS X)
    Reinstalled El Capitan and Yosemite
    Tried doing two partitions with a different copy of OS X on each
    Ran First Aid from inside El Capitan
    Ran First Aid from the recovery partition
    Booted in Safe Mode and ran First Aid where I get the following message:

    "Problems were found with the partition map which might prevent booting"

    I've tried running the hardware check thing by holding "D" during boot but it just got stuck again. After waiting on the grey screen for 20 minutes, I held down the power button to force it to shut off.

    So far, nothing has seems to make any difference. The only way I can get it to boot reliably is when in Safe Mode.

    I've searched all over and can't find any solution.

    Does any one have any ideas to help a fellow out?
  2. Fishrrman macrumors G5


    Feb 20, 2009
    Could it be that the drive itself is "wearing out" (hardware failure, in this case perhaps bad media on the part of the drive where the partition info is usually stored)?

    Here's what I would try:
    - Get an external drive the same size (or larger than) as your internal drive (I recommend that you get a USB3 drive -- perhaps even a USB3 SSD drive)
    - Use CarbonCopyCloner or SuperDuper to clone the contents of your internal drive to the external drive
    - Boot and run from the external drive for a day or two (at least)

    Do the old problems persist?
    Or, do they "disappear" when booting and running from the external?

    If they persist, sounds like "something in software".
    If they vanish, sounds like a hardware problem with the internal drive itself.

    Be aware that you can keep using the iMac (even if the internal is bad) by booting and running from the external drive. Your boot times (via USB2) will be a little slower, but -- once it's up and running -- you probably won't notice much of a speed difference.

    If you don't want to put money into a 7-year-old iMac, perhaps it's time to start looking for a replacement...
  3. hardhatmac thread starter macrumors regular


    Jun 13, 2006
    Hey Fishrrman,

    Thanks for the reply. I thought the same thing and that's why I replaced the internal drive. I'll still try it from an external but I'm starting to doubt it's a problem with the HDD. But, I guess it's not all that uncommon for two drives to fail in a row (even if one is brand new.)

    I'll report back after I've tried an external boot drive.

  4. bradc82 macrumors newbie

    Jul 31, 2018
    Hey Hardhatmac,

    Did you find a solution? I have the exact same issue and it's driving me mad!!
  5. hobowankenobi macrumors 6502a

    Aug 27, 2015
    on the land line mr. smith.
    Try an external if you can.

    Have not seen it on an iMac, but some MBPs would have the SATA cable fail, and lead to similar issues. Booting to external would rule this out.

    Have to partition Mac OS Extended (Journaled) on GUID, or it may not boot:


    Also....I had some iMacs at work that would hang on boot for a very long time. But only on 10.11. On 10.10, or 10.12, no issues. Something would hang on 10.11. Never figured out what: software conflict, third party something...firmware version for specific hardware....don't know.

    But you might try another OS to rule it out.

    Booting into Safe Mode is a good sign. If it would not boot at all, to any OS, I would suspect a hardware fault beyond the HD.
  6. bradc82 macrumors newbie

    Jul 31, 2018
    I can boot to an external drive but the computer soon freezes up and stops completely so I assume it's a bigger problem than the HD unfortunately. Thoughts? Thanks

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