After removing the video card, the next step was to access the CPU fan. In the picture on the right you can see the Microprocessor Thermal-Cooling Assembly starting with the CPU fan at the bottom middle, running over the northbridge copper heat transfer pipe, and finally to the CPU heatsink. This Aluminium block has two copper pipes running to the left and right fans, for extra cooling.
Once I had got this far, I suspected the blockage was after the fan, but before the Aluminium block. I removed the video card (as you saw previously) and then the four screws on the block.
The block gave a bit of resistance, and then lifted. Experts would recommend you do this to a hot machine, and this is the reason why: There's the CPU nicely stuck to the block. oops! The CPU pulled right out of the closed ZIF socket! Note that you can't do this to a warm laptop, unless you're fast, as it takes time to get this far.
There's a great thread here about removing a stuck CPU. I think the dental floss is a bit over the top (and time consuming), so I used a heat gun. I placed the assembly upside-down so the CPU wouldn't fall off, and blew the heat gun (or hair dryer) on the two end fins. Stop when it's only just too hot to touch. Then only a tiny bit of pressure was required to lift the CPU. Don't apply pressure to the corner of the CPU with a screwdriver!
Here's the final shot showing no CPU or video card.
Make sure you cover the ZIF socket with something to keep it dust free. And don't touch the CPU or heat sink heat transfer surface, as your skin-oils can deter the heat transfer.
Here's the cooling assembly. You can see the thick dust covering the channel. There was also dust all through the fins. (Again, sorry for the bad photos).
Now I cleaned the CPU surface and heat sink surface with alcohol and a lint-free cloth, and applied a covering of Arctic Silver. The next two photos show why it needed cleaning:
And now it's time to reinstall! Follow the pull-apart instructions backwards.
Take careful note of where the screws go as some screws were different sizes to the ones listed in the Dell guide. Also make sure you take care with re-inserting the parts. I cracked the display bezel and one hinge because I couldn't fit the centre hinge cover properly. Nevermind, they're only about US$25!
On the right you can see a gcc compile at 100% CPU usage. The CPU has only just started to heat up at 43 degrees C. It didn't pass 58 degrees after compiling my system for hours, and the fans were all at low / medium speed.
Finally, at idle, it's now 40 degrees C. (woot).
Oh, and by the way: I suspended before taking out the CPU, and I resumed days later without any software issues!