It won't restart unless I wait an hour. Also crashed after 30 min when in target disk mode. Disk utility said no problems. I'm using system 10.10.3
You should run the Apple Hardware test from your original gray install discs.
Thanks, Mike. I ran the hardware test - No trouble found. Any other ideas?
Run it two or three times in extended mode. AHT isn't the most reliable tool but it's all they give us. When you say your mac crashes what does that mean? Is it having a kernel panic? OS X: When your computer spontaneously restarts or displays "Your computer restarted because of a problem." - Apple Supp…
Post a panic log Mac OS X: How to log a kernel panic - Apple Support
I should say that it freezes. Just stops, get the spinning beach ball of death... I need to press the power button to turn it off. If I don't wait about an hour before restarting, it freezes during restart. That's maybe the oddest part of the whole thing. When it's "on" I ran disk utility OK. However, after a freeze, if I boot with the OX Install CD, disk utility doesn't "see" the hard drive.
I tried resetting the PRAM just for the heck of it, but it doesn't seem to take because it doesn't like to restart right away (time wasn't affected).
Never seen anything like this one! and thanks again for your help.
My best guess is that your hard drive is failing. If you haven't you need to back it up NOW before you can't. If you have an external disk that you can install OS X on and boot off of that to test you can either prove or disprove the hard drive failure. It sounds like the drive is getting hot and locking up. Or worse a connection on the logic board is getting hot and opening up.....hope thats not the case. Hard drives aren't difficult to replace.....and you can replace it with a blazing fast SSD if that turns out to be the problem.
I guessed as much... OK, the extended hardware test showed an error: 4HDD/11/40000004: SATA(0,0)
Failing hard drive. Sorry. But like I said not that difficult to change. https://www.ifixit.com/Guide/iMac+Intel+24-Inch+EMC+2111+Hard+Drive+Replacement/ 5211
iMac 2008 always crashes after 30 minutes.
