This article is applicable to Lenovo 3000 series and Y410 models.
If you find that your fan is running more often or at higher speeds than it used to, or your system is running warmer than it used to, it could be a sign that the fan and heat sink could be clogged with dust or lint. As air is drawn in from the bottom on these systems and then blow through the fins of heat sink before exiting on the left side of the system, just or lint may be drawn in more frequently if the system is frequently operated on a bed, blanket or other cloth surface, or in a dusty environment.
If your system is out of warranty and might be running warmer than normal as described above, you might clean the fan and heat sink to lower system fan speeds and operating temperature.
First, remove AC and battery and turn system over. Locate the fan cover.
Remove the 2 screws and lift up the cover from the edge.
Next, remove the 3 screws marked by the arrows to remove the fan - carefully locate and uplug the fan connector from the system board as you lift it out.
After removing the fan, it should look like this...
Using a can of compressed air, blow out the area, blow the dust out of the fan.
Clean out the heat sink fins by blowing air through the outside vents so that the dust is blow back toward the the fan locations. Make sure the fins are all free from lint, fibers and dust.
After all dust has been cleared out, carefully reinstall the fan and 3 mounting screws. A magnetic screwdriver can make this operation easier. Don't forget to plug the fan back in.
Reinstall the outside cover and screws. Reinstall battery and AC and power up the system.