A case can help protect your MacBook from bumps and scratches, keeping it in good cosmetic condition and protecting it from more serious damage. A poorly designed or inappropriate case can stop air from circulating, however, leading to problems with overheating. If your MacBook is overheating in its case, the case itself may not be the culprit -- issues such as blocked vents can also cause your computer to overheat.
Normal Operating Temperature
It is normal for MacBooks and other portable computers to become warm while in use. Areas near the screen's hinge can become warm, as can the base. If your MacBook is becoming uncomfortably warm while resting on your lap, move it to a stable surface, or use a cooling pad.
What is Overheating?
While a rise in temperature is normal, too much heat can impair your MacBook's performance and may cause lasting damage. Signs that your unit is overheating include slowing down, freezing and shutting down unexpectedly. The MacBook's internal monitoring capabilities let it recognize dangerously high temperatures and perform an automatic shutdown. Repeated or prolonged overheating can damage the MacBook's internal components and may affect the useful life of your battery.
Overheating in the Case
Cases can increase the tendency of any portable computer to overheat. They can form an insulating layer around the unit so that heat does no disperse away from the case; thicker materials will make this worse, as will materials with greater insulating properties -- hard plastic may be better than foams, which trap more heat, while metal cases conduct heat and disperse it. A case may also obstruct the Macbook's vents, blocking the air circulation that helps keep the device cool. This is especially true of cases not designed for use with a MacBook, as these may be poorly designed. Your case should have stand-offs ("feet") to lift the base of the MacBook clear of the case so air can circulate underneath it. The case should also be vented to allow warm air to escape and cool air to be drawn into the MacBook. Do not keep other items such as papers inside the case, as these can block air circulation.
To find out if the case is at fault, remove the MacBook and run it without the case. If it doesn't overheat, then your case is probably the culprit. Use the MacBook without a case or try a different case, preferably one designed by Apple for your particular MacBook model. If the computer continues to overheat, the case is not the problem, and you must continue looking for a solution.
Other Causes of Overheating
Keeping your MacBook's software and firmware up to date can help stop overheating. Resting your MacBook on the couch cushions or propping it on your comforter as you read in bed may be tempting; however, soft surfaces obstruct vents and stop air from reaching the base of the unit. Place your MacBook on a desk or table, or invest in a cooling pad. Another cause of overheating is an obstruction in the vents; dust, foreign objects and sometimes the protective film applied by the factory can all block vents and contribute to overheating. Check that all the vents are clear; if they are blocked, turn off your MacBook, disconnect it from the power and remove the battery. Remove any foreign objects that you can see, and use compressed air to blow away dust or wipe the area very gently with a soft lint-free cloth. If this doesn't resolve the problem, seek professional advice.
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