Everybody knows that, I know, but I was wondering why my machine was making a lot of noise like a jet turbine, and eventually just shut down without any warning during rendering.
I use to clean the cooling fan carefully with a vacuum cleaner from time to time, but never thought of looking behind the fan. The ribs were almost completely covered with dirt, so no wonder that my machine refused to work. Using a brush together with my vacuum cleaner made my life happy again.
Before I did that I could hear my computer howling like a wolf from any other room. Even with closed doors. Now it's gently purring like a kitten.