MacBooks consume power when running and it dissipates as heat. However, if it gets too hot electronic components fail and so each MacBook has a cooling system to control the temperature of vital components.

The cooling system usually consists of a heat sink clamped to the processor and fans to draw cool air into the case via side vents and force it through cooling vanes on the heatsink and expel the hot air out of the case usually via the hinge line. The fans can reach a roaring 6000rpm but if they look like the fans in the photo that wont produce anything but noise. These fans can spin all they want but they wont move air when fluff fills the fan blades.

Besides risking failure through overheating, this MacBook is at serious risk of corrosion with an internal source of liquid! The debris inside this MacBook is a food source for insects and mollusks which expire when electrocuted and their moisture content results in corrosion which damages circuitry.

This MacBook, inspected during a battery change, desperately needs disassembly for a thorough internal clean to prolong its life.