Introduction: Computer (Laptop) Cooling Basics
The cooling of the CPU(Central Processing Unit), otherwise referred to as "The Chip" or to laymen "The Brain" of the laptop is a dilemma that most manufacturers have to face when designing a laptop enclosure (casing) and choosing the correct CPU for it. The cooling is normally performed by a fan and some kind of metal conductor like copper or aluminum called a heat sink. The CPU, and lately the GPU(Graphics Processing Unit), are "connected" to the metal heat sink via a thermal grease or compound. This grease conducts heat but not electricity. The "trick" for manufacturers is to get rid of as much heat as possible using as small a fan and heat sink as the CPU will allow. Vents are also cut into the casing allowing the fan to suck cool air from the bottom, force it over the heat sink and blow it out the side or rear thus cooling the CPU and GPU. In more modern times copper is being used as the conducting metal, liquid is "pumped" through the system and radiators and exhaust ports are used just like in motor vehicles. All this to get rid of the heat and make the system run faster.

The Problem
The problem is that over time dust and other particles clog the vents, fan and exhaust port or radiator of the system thus restricting air flow and cooling. This is fixed relatively easily by blowing out the vents and fan with air or using a brush or earbud (Q-tip) to clean away the dust. Remember: In the computer world - DUST DESTROYS! There is however another hidden problem that occurs when computers (laptops) heat up or overheat. They tend to dry out the thermal compound that conducts the heat thus causing the system to overheat more quickly. Luckily most CPUs, GPUs and chip manufacturers have built in protection for this. They step down the operating speed bit by bit until they eventually switch off the CPU and thus the system shuts down. So if you have a computer system that starts working slower and slower and then switches off for no apparent reason, overheating could be your problem.

The Solution
To solve the overheating problem, especially in laptops, I am going to show you how to get to the cooling unit, dust it out, replace the thermal grease and put everything together again. In order to demonstrate this I will be using a friend's LG F1 Pro Express Dual laptop that started exhibiting just such symptoms. It would become sluggish and then suddenly switch off for no reason. This caused him a lot of lost work and a corrupted Outlook PST email file. Here I will show you step by step the solution to this nasty problem.

Interesting Tech Fact: I captured all the pictures with my Samsung Galaxy S cellphone.

Step 1: Preparing for the Process

Before you start, make sure you have made a backup of all your data files and that if in the unlikely event that something does go wrong, you will be able to restore your application programs and the data. (Tip: Test the data files to make sure they were backed up correctly!)

Make sure the backup is totally separate from your laptop, not on the same hard drive, on an external device like a SD / USB or portable drive.

Prepare an area to work on that is well lit, clean, dry and has enough space. Use a towel or soft cloth under to laptop to protect it because it will be lying on it's screen for most of the time during the procedure. Make sure that nothing you use, even your clothes, generate static electricity. This process will take about 30 minutes.

NOTE: THIS WILL VOID YOUR WARRANTY IF YOUR LAPTOP STILL HAS ONE. ASK YOUR SUPPLIER TO DO THIS FOR YOU IF IT IS STILL UNDER WARRANTY!

Step 2: The Tools

You will need the following:

Tools:
1. A holder to keep the screws from getting lost. (The cap of a deodorant can works well.)
2. Thermal grease or compound. You local computer shop or hardware store should have this otherwise "Google is your Friend"
3. Screwdrivers that fit the screws on the back of your specific laptop.
4. Earbud (Q-tip) cotton swabs
5. Wooden tongue depressor or any other soft object to scrape the old thermal grease off.
6. Brush

Time:
About 30 minutes

Cost:
A couple of Bucks

Saving:
Huge! (You would normally have replaced your laptop as it is unusable in it's current state.)

Optional:
Rubber gloves or finger cots
Earth strap or grounding wire
Some Isopropyl alcohol wipes

Step 3: Removing the Battery and Back Cover

After you have backed up all you data files and shut down your laptop, unplug the power source and remove the battery. In the case of the LG F1 Pro Express Dual the battery is released by two clips, marked 1 and 2, in the second picture. The system door has 4 screws that give you access to the CPU, GPU, RAM (Random Access Memory) and various other parts like the Real Time Clock battery, modem and cooling unit.

Release the battery and remove it completely. Using the correct screwdriver loosen the four (4) screws. Place then in the holder once they are removed. Remove the back cover and set it aside. You will notice dust clinging to the back cover. Use the brush and earbuds to clean the vents and back cover.

Step 4: Unscrew and Remove the Cooling Unit

You can now put on your rubber gloves and attach your grounding/earthing strap if you want to. I did not.

The easiest way to identify the cooling unit is to look for the fan. Once you have this, it should be easy to locate the screws holding it down. Carefully remove them and place them in the holder. Gently grip the cooling unit and remove it from the laptop. Try twisting it back and forth, left and right, slightly (not up and down) before lifting it out. It should "break" any hardened thermal grease that acts like glue. This one comes out at a slight angle. Remove it slowly and gently because the fan power cable is still attached to the motherboard and needs to be removed before the unit will come out completely.

Note: In my case, the CPU came out with the unit. This is unusual and very rare as the CPU is normally latched firmly to the motherboard. In my case the thermal grease had dried out completely and acted like "putty" by "glueing" the CPU to the heat exchanger. The twisting action should "break" this glue bond but is not always possible. Open the CPU socket "latch", take the CPU by the edges. DO NOT TOUCH THE PINS! Align the CPU to the socket by matching the markings or pin configurations together. Press down firmly to seat the CPU and lock it in place with the latch.

Step 5: Dust Out the Unit

Using your breath, compressed air, hair dryer or fan gently blow out the dust located in the fan, case, exhaust port and anywhere else you see it accumulated. Use earbuds to clean the fan blades. Hold the fan down when blowing it with air so that it does not operate in the reverse direction and also not work against the blowing air. Use the brush to dust everything off one last time before blowing it out with air again.

Step 6: Remove the Old Thermal Grease

Using a soft object like a wooden tongue depressor, plastic knife or old credit card scrape the old thermal grease / compound from the CPU, GPU and Heat Exchanger. Be gentle and take your time as there is no rush and trying different angles, the dried thermal grease should just flake off. Here you could also use the Isopropyl alcohol wipes or an earbud dipped in Isopropyl alcohol to remove the dried thermal grease. It comes off easier then. If you are going to work and touch components on the motherboard, I suggest you wear an earth / grounding strap and rubber gloves.

Step 7: Apply New Thermal Grease

Place a very small blob of thermal grease (mine might be a little too much) on the CPU and GPU only. Do not place any on the heat exchanger as well. You only need to place thermal grease on one or the other. Use the wooden depressor, plastic knife or old credit card to spread it evenly and very thinly over the surface of the area of the CPU / GPU or heat exchanger that will come in contact with each other. More is not better in this case. Too much thermal grease will not cause better heat conduction but might even cause some heat build up.

Step 8: Replace the Unit and Close the Case

Connect the Fan Power Cable. Replace the heat exchanger and tighten down the five (5) screws to keep it securely in place. Replace the system door, pressing down gently but firmly until all the sides have clipped in place. Replace the four (4) screws and tighten them. Replace the battery and make sure it is locked in place.

Step 9: Turn the Unit On

Plug everything back into the laptop that needs to be there and turn the unit on. Voila! No more overheating. Its a miracle you have given your laptop a new lease on life!

Step 10: Tips and Additional Resources

In conclusion some tips and additional resources to help you manage, reduce and monitor your laptop overheating problems.

Use your laptop on a hard flat surface. Blankets and clothes tend to block the vents and reduce airflow.

The help reduce heat build up even further you can use a laptop cooling pad. This usually raises the laptop and has fans that force more air in from the bottom.

If sudden laptop shut-downs have also damaged the Outlook PST file, use MicroSoft's SCANPST to fix it. SCANPST can be found here for the different versions of Outlook:
http://www.msoutlook.info/question/77

More Outlook repair tools can be found here:
http://www.howto-outlook.com/products/outlooktools.htm

If you suspect your system of overheating, CPU and system temperature can be monitored and logged by this FREEWARE program called SPEEDFAN.
http://www.almico.com/speedfan.php

Keep those laptop's cool!

Step 11: Afterword

Testing the Temperature
Quite a few people have commented that I used way too much thermal grease (compound) and that the amount I used would cause overheating. I disagree with this view. So in an attempt to provide some kind of proof, one way or the other, I decided to monitor the temperature for a few weeks with SpeedFan v4.44. Then to take the laptop apart again, clean it up, using the suggested alcohol wipes method, and replace the thermal compound. This time I would use a thin amount. I would than assemble everything and then monitor the temperature again. I followed the same process as before with the slight suggested changes. This documents that process.

According to the CPU chip specifications for a LF80537 T5500, which is a Intel Core 2 Duo Mobile, the Minimum/Maximum operating temperature (°C) is 0 - 100°C. The maximum operating temperature of the CPU was 65°C before I started this process. After I completed the process the maximum operating temperature was 60°C. It seems I might have applied too much thermal compound but not way too much to cause overheating. Just too much as in wastage. It would seem as if excessive amounts of thermal compound could cause your system to heat up slightly more and if it is running close to the maximum allowed temperature it might cause overheating. It caused a 5°C increase in temperature in my case but this is not definite because it was not a controlled situation. The increase was not enough to cause overheating, but enough to deduce that excessive amounts of thermal paste could increase the temperature. The photos contain a step-by-step guide of what I did.

Notes: Wipes

I found the alcohol wipes worked terrible. It smeared the thermal grease all over and just created a bigger mess to clean. It could be because the previous thermal grease was al dried out and flaked off nicely. This thermal grease was wet and sticky. It smeared too easily. On the GPU there are very small resistors or components and the wipes smeared the thermal grease all over them and then kept getting caught in them.

If I were to do this instructable from the start over again, I would use less thermal grease from the start as it does make a difference no matter how slight, but I would not use the alcohol wipe.

Update 2013

I have been ripping Intel CPUs out of laptops and desktops and replacing the thermal compound (grease) for years now and have noticed that on the older Intel CPUs the thermal grease was used liberally. However, on the newer CPUs the compound is quite thin. I wonder if it really matters that much or is it cost saving to have a very small (tiny) amount of compound in between the CPU and the cooler (heat sink)?

Here is what Intel itself says about how to apply thermal grease to a CPU. What you will read will surprise you because there is no mention of layer thickness and no mention of spreading it around. To tell you the truth it states that you blob everything in the centre of the CPU and the pressure of the cooler (heat sink) on the CPU will determine the thickness, squeezing out all excess. I think I also mentioned something like that in one of my comments. This information comes straight from the CPU manufacturer, and they should know. Read for yourself at:
http://www.intel.com/support/processors/sb/CS-030329.htm (Click "How to Apply TIM" from the menu)

I have included some of the photos from the Intel site for reference.
I have also replaced the thermal grease (compound or interface material if you are from Intel) on many secondary chips like integrated GPUs on motherboards by releasing the cooler (heat sink), cleaning both surfaces, apply thermal grease and replace. Once you know how, you can replace the thermal compound on practically anything.

Update 2014

Many people are still suggesting I am using too much thermal grease. I want to bring the following to the attention of these people. I am using a non conductive thermal grease. It does not conduct heat as well as the conductive thermal grease but does not damage components when it comes in contact with them because it does not conduct electricity. Cooling has to do with getting rid of excess heat, so the thermal grease is only one part of the solution. The heat sink, fan and airflow are the other parts. You could have a CPU that does not have well applied thermal grease but has a fantastic heat sink and airflow across it and the system will never overheat. Here are some links to other resources which I found very helpful in understanding overheating, thermal grease, fans and airflow.

http://www.tomshardware.com/reviews/cooling-air-pressure-heatsink,3058-8.html
http://www.tomshardware.com/reviews/thermal-paste-heat-sink-heat-spreader,3600.html
http://www.tomshardware.com/reviews/thermal-paste-performance-benchmark,3616.html
http://www.bit-tech.net/hardware/2009/02/16/all-about-tim/1
http://www.intel.com/support/processors/sb/CS-028869.htm
http://www.intel.com/support/processors/sb/CS-030329.htm

I hope this helps everyone understand more about what causes overheating and how to solve the problem.

Step 12: How Much Thermal Paste Is Enough?

During the course of writing and expanding this article I have constantly been told that I use too much thermal compound or grease. Most of the people that make these statements have no proof either way of how much paste needs to be used. They also do not read the complete article with its comments. I have been doing this since the early 1980's and have never found the amount of TIM (thermal interface material/compound/grease/paste) I use to cause any problems. I normally provide a link to CPU manufacturer, Intel's, website where they explain how to apply TIM. Intel just state that you apply a blob in the middle and let the pressure of the heat sink spread it. I also refer people to Tom's Hardwarewere there is a much more in depth analysis on the application of TIM.

Although Tom's Hardware is quite thorough regarding the issue you will see that it is not totally impartial and personal the preferences of the tester do come to the fore. Like the statement that "smearing paste on the whole CPU is quite pointless and a thing of the past" because all CPUs have hot spots that generally lie like a sausage in the middle of the cpu from left to right. However, Tom's admits itself that it is not that simple in their statement "The two images below illustrate what a hot spot is, albeit in an over-simplified way. Reality is not as simple; CPU cores may be loaded differently, and there is also the issue of on-die graphics, which may be more or less active than the processing cores." This means we do not really know exactly where the hot spot really is at any given moment. Tom's even admits that the application method is a "philosophical debate". Although Tom's stated previously that spreading paste on the whole core "is quite pointless and a thing of the past" they then discuss Revoltec Thermal Grease Nano which is applied with a brush. A picture is shown where the whole CPU is "painted" with the paste even though it is "pointless and a thing of the past". Tom's states that "these pastes typically fall to the bottom of our performance charts. When you try to apply semi-liquid pastes by brush, typically you wind up with too much, and that isn’t optimal." Then Tom's states that spreading is tedious and runs the risk of applying too much.

I am a firm believer of spreading a liberal amount over the entire surface that comes in contact with the heat sink. The reason for this is that I believe in the the law that states the maximum heat transfer happens when the biggest area is touching the conductive material.

NOTE: NOT ALL TIMs CAN BE SPREAD BY HAND!

In an effort to provide a more believable answer than just my experience and opinion, I have gathered some pictorial "evidence" of how the manufacturers of the chips themselves apply TIM. At www.hardwaresecrets.com they tested the outcome of the amount and method of applying TIM by applying a tiny dot in middle, a small dot in middle, transversal line, parallel lines and spread across the CPU methods. Although the tests are not 100% lab proven the do give and idea of what to expect.

The results in core temperature in Celsius were as follows:

a tiny dot in middle - 55

a small dot in middle - 50

transversal line - 51

parallel lines - 51

spread across - 51

The difference in applying too much paste to just the right amount is 1%. The difference between applying a dot in the middle and spreading it is 0.2% and can be ignored. Read the article as the "correct" dot amount for them is also a bit of trial and error. I will then rather stick to my spreading method.

Make up your own mind based on the this information, the kind of paste you have, the kind of CPU and the heat sink that is to be used.