Model A1224 / Mid 2007 and Early 2008 / 2, 2.4, or 2.66 GHz Core 2 Duo processor

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Random crashes, unable to detect harddrive for a few hours after crash

Summary of symptoms:

  • Constant loud fan (starts after around half an hour after boot and does not stop)
  • Overheating (not so serious after starting to boot from external hdd)
  • Random crashes (usually when running demanding apps)
  • Random black screens + crash (usually when playing video, not happened since booting from external hdd + added RAM to 4GB)
  • Question mark folder every time after crash (but will be able to reboot after leaving it for a few hours)
  • Cannot boot from install DVD after crash (booted and ran for 5 mins then it crashed, 2nd time, black screen and disk keeps running)
  • Cannot wake from sleep (need to shut down using power button)

Tried:

  • Adding RAM - some help (as above and below)
  • Reinstalling OSX - no help
  • Repairing permissions - some help (as above and below)
  • Checked HDD w/ disk utility and disk warrior - no problem detected
  • Booting from external hdd - some help (as above and below)

The story:

I first noticed the problem with my iMac (early 2008, 20", 2.66Ghz C2D, 4gb RAM) when it couldnt wake from sleep. I used to put it to sleep every night (and use it as my alarm clock) I will shut it down when I go to work but I would forget every now and then. Could I have fried the logic board by constantly keeping it on? I started to notice it heating up and the fan running wild in the summer.

It really hit me when it crashed while I was using Garageband a few months ago. The iMac was boiling hot at the top left corner. After a couple of crashes (I had to shut it down by holding the power button), it gave me the question mark folder at start up.

I thought it was dead because I couldnt even boot from install DVD to repair permissions. but when I tried my luck after an hour, it came back on and I could back everything up, repaired permissions, checked disk, did a quick disk defragmentation etc.

The next day the same thing happened again. Thank God it did let me to finish up my project. Then I didnt use garageband and thought it would not crash again.

Then it started to give me sudden black screens (when i was watch videos - youtube or simply playing video files) forcing me to shut it down using the power button every time (no response, cannot use shortcut to shut down).

Every time i force shut it down, it will give me the question mark folder for a few hours. Repairng permissions will make it last longer before the next crash, but it does not solve the problem.

I used to use cleanmymac but heard that it will corrupt the systm. So i tried reinstalling OSX again. Didnt help. Crashes again when I tried to run bigger programs (iphoto, microsoft office ...)

Then I decided to add more RAM. Upgraded from 2GB to 4GB. Did make it last longer before crashing on me again, black screen and all.

I couldnt stand having to wait a few hours before I could boot my computer again so I installed OSX on an external hdd and booted from there.

Thought everything was fine. But the next day when I was using word it gave me the spinning beachball for around half an hour (no black screen), and when I tried to record more tracks on Garageband one day, it crashed on me again. Not sure if it could be due to the speed of the usb port / speed of the external hdd.

With my external hdd, I don't have to wait for a few hours for a reboot after a crash. My iMac can detect the external hdd fine even after it crashes. But the internal hdd will disappear for a few hours after a crash and reboot.

Sound like a logic board issue? Will it help if I replace the internal HDD?

Any help will be much appreciated!!

Answered! View the answer I have this problem too

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Chosen Solution

Use Time Machine and back up your internal hard drive, then replace the drive.

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Comments:

thanks for the quick answer. i checked the hdd before with disk warrior and there seemed to be nothing wrong with it... assuming that it is dead, can a bad harddisk cause all these problems? e.g. not being able to wake from sleep, can't even boot from install dvd, black screen etc.

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Disconnect the hard drive and see if you can boot from the installation disk.

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thanks a lot! i finally decided to replace my internal hdd. it seems to be fine so far. though did seem fine last time i reinstalled osx as well, but then it gave me black screens all over again after a while. hope it really did work! fingers crossed!

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i am not sure if it gave me a black screen a few days ago. i restarted my imac and repaired permissions. seems to be working fine again. i havent been doing much on garageband these days. will continue to wait and see what happens. thanks a lot for your help.

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hi there.

the problem came back after just 3 months....

this time i tried to apply fresh thermal paste on the cpu and gpu.

the cpu temp is fine now but the gpu is at 80C+ even just after startup

i heard that lion causes overheating problems so i tried to install snow leopard - but i cannot get past the installation process without it blacking out again.

any thoughts would be greatly appreciated!

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Steph will be eternally grateful.
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