Since we see quite often people here in forums asking for help regarding YLOD, I wanted share my alternative method for repairing YLOD since I consider it to be easier and it doesn't require complete dissassembly. This method has also worked for GLOD(green light of death - all lights seem normal but no video/audio output and controllers won't sync). I have sent email to gilksy some time ago to get my method to his guide, but since he hasn't replied I decided to post my method here. I actually discovered this first time some time before gilksy published his guide but since hadn't much experience using this I didn't post this.
Since problem is very similar to xbox's RROD the fix fundamental is similar: add pressure to GPU and CPU. I tried various things(shim etc.) before I figured out what would be the best solution for adding pressure.
I come across following solution:
You need just 4 big washers(diameter 40mm, hole 8mm and 1mm thick. You can find these every hardware store for less than 1euro.) to do this.
So you have to remove upper cover, blu-ray drive and PSU. It's fairly easy and you can find tutorials for it from this site or youtube and I don't cover it here.
What you have to do is to put washers on the screws which holds the cooler blocks in place.(arrows in the photo)
Just screw screws as tight you can get them with reasonable force. I recommend using turn by turn technic so that both screws gets about same amount pressure whole time. You can't screw them too tight because of type of the screws.
You have to cut out small piece of one washer(which goes to screw on lower right in photo) due metal clip used for attaching PSU and memory card reader. Dremel or something similar is good for cutting.
Because of washers thickness it adds some pressure and because washers size it produces pressure from larger area.
Adding these washers have been enough for all PS3s I have come across. I'm sorry because I don't have any photos of washers assembled since I don't have any unit under repair right now and I have lost my old photos regarding my repair method...