Temps causing problems? 24" iMac, mid-2007

I just took the iMac apart again and looked over everything. The GPU does look to come apart from the main logic board. There are a couple screws that keep it connected to the main board. I guess I could try replacing the GPU, and then if that doesnt work, replace the logic board. Then if neither of those work, visit the Apple store for a new iMac.

Good news.

I bought a used GPU heatsink off ebay for $5 and bought some Arctic Silver thermal paste from Amazon for $10.

I replaced the heatsink and used new thermal paste, and after 90 minutes of having my son play Minecraft on it, the fans arent spinning fast and the GPU temps are staying around the 120 (f) mark.

Before, after about 5-10 mins of the computer sitting idle, the temps would have skyrocketed.

I hope I am not speaking too soon, but so far, this looks promising. I dont know if the problem was a bad sensor, heatsink or thermal paste, but for a $15 repair, I dont care which was the problem. I might have just gotten another year of life out of this thing.

Hi James. It has been a while since I did this, so I am going from memory, but this is what I did.

I checked prices of a brand new GPU w/heatsink from Apple, and it was incredibly expensive.

So I started trolling through Craigslist and ebay and finally found someone selling a used heatsink without the GPU for my model of iMac. I bought it for $5 on ebay. I thought it was an incredible deal, and I wouldnt waste much if it didnt work.

So I got the replacement heatsink and bought some thermal paste off Amazon that everyone recommended. It was called Artic Silver.

Once the heatsink and thermal paste came in, I tore it all apart using instructions I found on ifixit.com

Here is the site I used to figure out how to tear it apart:

http://www.ifixit.com/Guide/Replacing+iMac+Intel+24-Inch+EMC+2111+GPU+Assembly/5 214/1

This is the thermal paste I bought:

http://www.amazon.com/dp/B0002EQU6C

Once I did all of this, I reassembled it (breaking my infrared sensor in the process) back, turned it on, and all the problems I was once having completely went away.

Here is what I dont know. I dont know what was really bad. It could have been a bad bonding with the thermal paste. It was all cracked and dried out on the old heatsink, so maybe just re-pasting it would have worked?

It could have also been the thermal sensors that are built in to the heatsink as well. I had no way of testing whether they were working or not.

All I know is that by replacing the heatsink and re-thermal-pasting it, my iMac is now back to normal.

I hope this helps.

I have thoroughly cleaned the iMac twice in the past few months, so there is no dust in there.

Is the video card part of the logic board, or is it a seperate component?

One more sign of success. It succesfully passed the extended Apple Hardware Test and has now been running for 6 hours with no problems at all. Neither of those were possible before I repaired it.