In my old (really ?) macbook pro 2008, the right fan was very very noisy. As it's not a sufficient reason to renew this computer, I decided to change the fan. But getting a new one was a bit expensive, much more than I expected. However I had an idea but no tools to unmount my laptop.
Thinking of the dust there could be inside my computer, which is now always closed and plugged to an external display, I decided to clean the fan. The driver kit helped me to remove all the screws with ease. Then I just put one (and only one !) drop of lubricant on the axis of the fan. That does the trick !!
Let the lubricant get inside the axis of the fan. Only one drop will be necessary and as there will be no more noise (better than before), you can check the fan speed with a software.