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 http://www.hwinfo.com/.  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 http://www.passmark.com/products/bit.htm.  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.

Fixed.

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

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