The case of the overheating Minecrafter

My daughter loves Minecraft.  She came to me last week complaining that the computer she plays on kept turning off.  Time to fix it. 

I knew right away what the problem was from the death rattle in the case. The CPU fan was dying.  Easy fix.  I went to Best Buy and bought Antec 80mm fan.  Installed it and Viola.  Fixed?

Not quite.

The box still kept shutting down.  Odd.  I have been meaning to install another video card in it, so I swapped in a new (old) video card and a new (old) 500 watt power supply.  Fixed?

No, still not fixed.

Time to do this the proper way, actually diagnosing the problem instead of just throwing parts at it.

I downloaded and installed HWInfo from  This app told me the power supply rails were fine, but that the CPU was running really hot.  Really HOT!  it was at 70C just running Windows.  Bad times.  Before I tried anything else I wanted to be sure that overheating was the problem.  I installed the demo of BurnInTest from  Running the CPU test the temperature quickly climbed 78..79... 80... and powered off.  So that's definitely the problem.  The PC is shutting down to keep from cooking the CPU. 

I had a shiny new blue-LED for-extra-coolness Antec Fan on it, why is it overheating? 

... Because I neglected one important step.  When I pulled the heatsink to replace the fan I neglected to replace the heatsink grease.  Crap.

I headed back to Best Buy for some thermal grease.  Back home, I cleaned off the old crud on both the chip and heatsink with Q-tips and Rubbing Alcohol.  I then put on a thin layer of new thermal grease and screwed the heatsink back on.

Firing the machine back up, It stays at 55C when running a CPU burn-in test now with the fan control set on the lowest (quietest) speed.  Fantastic.  I did a quick experiment to see if pulling air through the heatsink or pushing air through the heatsink would result in cooler temperatures.  Pushing air through the heatsink was the winner by 2 degrees.


Lesson Learned: If you pull a CPU heatsink, replace the thermal grease.  It can easily make a 25C+ difference.