What this fix involves is nothing but mere screws and washers. Seriously, no overheating your console, adding new fans(although you can add them if you like), or towels. Ever since I installed it I haven't had the console freeze up once.
Step 1: Before we begin...
For starters, why would you need to repair the console yourself? If you have a working warranty, I highly suggest you send the console to Microsoft for repairs,as a repair will void your warranty. While Microsoft dropped the ball on product quality in efforts to get the 360 out before the other consoles, they picked up the proverbial dirt-covered ball by extending all warranties to 3 years.
If you plan on actually reviving the 360, don't use the towel trick. What it does is overheat the inside of the console by blocking fan intakes, temporarily doing something to make the 360 run for a brief period of hours to days. While it may be the quick and easy approach, it also overheats every other component in the 360, which is never good. It can cause chips to fail, capacitors to dry out, release the magic smoke, and possibly spark a fire. So unless you hate your Xbox something fierce, don't do this.
And of course, if you're on your 4th Red Ringed Xbox 360, and are considering buying a PS3...
FIX IT, REGARDLESS OF WARRANTY!
I would hate to see someone give up the pinnacle of gaming due to a simple flaw, over a Blu-Ray player with gaming functionality.
So, if your warranty is void, or you're about to join the dark side of gaming, read on!
Step 2: The Suspected Cause
The problem is pictured below.(the second image, silly) Those two X-shaped pieces of metal are what try to hold the heatsinks onto the CPU and GPU. Problem is, they aren't springy enough to do the job. The heatsinks have a tiny amount of wiggle room, and the motherboard is free to warp from heat. That prohibits proper heat dissipation, and allows the processors to break away from their connections. I blame bad design from Microsoft's need to get the 360 out before the PlayStation 3. But now isn't the time for blame, I bet you're about ready to buy one of those Blu-Ray players that come with gaming functionality.
So now we've determined that those "X-Clamps" need to go. The next step lists parts needed.
Step 3: Parts and tools needed
4 5x20MM Panhead Machine Screws (Keep length between 20 and 40 MM)
4 5x15MM Panhead Machine Screw (Must be no longer than 15MM!)
44 #10 Washers
And for your English measurements (Thanks to ajmontag for providing these):
4 3/16" x 1" Panhead Machine Screws
4 3/16" x 1/2" Panhead Machine Screws
44 #10 Washers
These 5x20MM(3/16"x1") screws will be used to secure the CPU heatsink.
The shorter screws will be used for the GPU, and 15MM is the most you can get into it. The 1/2" fits just fine with room to breathe.
About 44 #10 washers. These will be used to keep the motherboard firmly in one position. Nylon washers aren't necessary, there are no traces or components to be touched around the screw holes. But if you feel you must have them, I will not stop you from purchasing them.
And while you are working with the heatsinks, you may want to apply new and better thermal paste to them. I suggest picking up a tube of Artic Silver 5.
Toolwise, you'll need:
A drill or drillpress to widen screwholes in the metal case(with a 3/16 drillbit)
A torx 9 and torx 6 screwdriver to remove screws from the 360's case
A 1/4 inch wrench or socket to remove the X-Clamp posts from the heatsinks
A phillips-head screwdriver for those machine screws(or flathead if that's what you got)
And a tiny flathead screwdriver to pry off the X-Clamps.
Anything else like tape and steel scrubbers should be kicking around in your house.
Step 4: Gettin' to buisness: Remove the heatsinks
You need to remove everything from the metal case(if you can't get the fans out, that's fine). Set the motherboard on a clean surface, like a newspaper. Put the DVD drive, screws, plastic case and other parts someplace where they can't get harmed.
Now you gotta remove the heatsinks from the processors. This is very nerve-wracking. I used a small flathead screwdriver, and pried two or three of the X-Clamp's legs from the posts attached to the heatsinks. But if the blade of said pointy object were to slip, it could take out a bunch of tiny parts as it scrapes across your motherboard. The solution?
Put a piece of corrugated cardboard over the motherboard, where the screwdriver blade would rip through. :D . So if it were to slip now, it'll just hurt a severed piece of a box.
You'll want to pop off 3 of the bracket legs, because the 4th one won't have anything holding it on. Once you get the clamps off, the heatsinks will come off on top side of the motherboard(you may need to tug on them a bit if the thermal paste is sticky). The next step deal with the heatsinks themselves.
Step 5: Stripping the heatsinks
Step 6: Drill bigger holes
To widen them, use a 3/16 inch drill bit with a drill press or hand drill.
If you're using a hand drill, set a wooden block under each hole as you drill it, to avoid warping the case. If you're using a drill press as I did, there should be a steel pedestal with a hole for the drill bit to pass through, saving the case from serious FUBAR-age.
Have the bit spinning before you push into the center of the hole. Repeat this for all the holes. Make sure there are no burrs left on the holes or shards kicking around in the case afterwards. Bang it around a few times to get them out, the last thing you'd want is to have your 360 die from little pieces of metal shorting it out.
Step 7: The Fun Begins: Screws, Washers, and more screwyness!
With the case sitting flat, fan hole in the back on the right, take note of where you need to stick these screws. the 4 holes on the left X are for your GPU, the 4 holes to the right will be for the CPU screws.
Now put the 5x15MM screws in the GPU screwholes, screwheads on the outside, so that they come into the case. Put tape over the heads to keep them from falling back out, as shown in the second photo. Now put the 5x20MM screws into the CPU screwholes, and tape them just like the GPU screws. This tape is very important, so don't take it off until I say so! Ha ha.
Lay the case flat again, and all the screws should be poking up at you, as they are in the main photo. Place 3 or 4 5MM washers on each of them, the idea being to get them level with the motherboard standoffs. Use a straightedge to check. If they come up too short or too high, the motherboard will get warped, and you won't be fixing anything.
Now the fun begins. You gotta get the motherboard back in the case, with the goal of getting the screws into those orange holes that the X-Clamp posts went through. All while you try to keep those washers on the screws! If they fall off at any point, you'll have to take the motherboard out, put them back on the screw(s), and repeat. So try not to do it, eh?
Tilt the case onto it's right side(where the hard drive connector would be), so that you can reach the screws underneath. Angle the back of the motherboard into the case, and push it all the way to the rear of the case. Lower the board until it gets held up by the rear CPU screws you installed(they should be the CPU screws if the screws were taller than the GPU screws). Now, untape one of those rear CPU screws, and point it into it's hole. Give it a few twists to hold it in place, and thread the other one in. Now, while carefully holding the motherboard and those untaped screws, lower the motherboard until more screws hold you up, and get them into their holes. Don't let those washers fall out!
When it's all said and done, you'll have screws poking through those holes. Tape the heads back to the case so they don't fall out. Now press on the motherboard around the screws, it should be solid at each screw. If not, you'll need to get back to those washers and pop another one on.
But if it's all nice and immobile, throw two washers onto each GPU screw, one onto each CPU screw, and head to the next step!
Step 8: Re-installing the heatsinks
Pick whichever heatsink you wanna put on first. Make sure the CPU's copper heatpipe is facing away from the GPU heatsink when you put in on. The GPU heatsink won't let the CPU heatsink on if you put it on wrong. The easiest way to get this right is to look at the smudge marks on the heatsinks, and match 'em with their processors. When you thread the screws on, start each one off lightly, then get them up tightly. Try to get them evenly tightened to avoid having too much pressure on one side of the processor, and too little on another. When it's all done right, the heatsinks should not move at all.
Now we get to test it out!
Step 9: Testing, testing, three, six, tee...
Turn it on without the fans plugged in, checking to see how fast the heatsinks heat up. Getting hot in less than a minute is excellent. Now plug in the fans and put on that plastic fan shroud. Turn it on again, and it should boot up normally, assuming you did the heat test(if you didn't plug in the DVD drive, the center LED will blink green).
If it goes RRoD instead, unplug the power cable, re-insert it and try again. If you cannot get the console to boot, press down on both the heatsinks with even force, and power it on again. If it boots, power it on with only one heatsink pressed upon. If it boots with that particular heatsink pressed on, power the 360 off, and keep re-booting until you find the problem corner(s) on the heatsink that need tightening.
The idea is to tighten any heatsink corners that aren't tight enough, in order to allow a good connection for that processor.
So if it boots up normally, and you can play a game for at least an hour without locking up, you've worked your magic, and the 360 can be re-assembled! Have a beer, rent a movie, eat some gummy bears, do whatever it is you do to treat yourself, because YOU DID IT!
The next step goes over some measures you can take to prevent overheating.
Step 10: Afterthoughts and Shoutouts
NOTE: There is word on the interwebz that Microsoft will ban you from Xbox Live for installing new fans. You have been warned.
Since there's no room to easily add a fan to the GPU heatsink, the next best thing you can do is optimize airflow. While the 360 has dual exhaust fans, most of the airflow goes to the CPU heatsink. By adding cardboard to the fan shroud and covering the top of the GPU heatsink as depicted, you can improve airflow even more, as you've just devoted a whole fan to it.
And if you really don't like the stock fans in the 360, you can always buy 3rd party replacements. There's Talismoon's Whisper brand of fans, with LED accents. I can't say anything on quality, as I haven't used one. But they seem to be quite popular. They can be found at http://www.Divineo.com .
And now onto the shoutouts.
Thanks to Google first and foremost. LOLz.
Xbox-Scene.com and it's members, for their endeavors in resolving this issue.
RBJTech for the idea of adding cardboard to the fan shroud.
Thanks to both those sites for all the info that I mixed and matched to create this tutorial.
Oh yeah, and a special thanks to Cheerios for providing better airflow than Microsoft could.
-Dr. Professor Jake "Biggs" Turner