In case that you think the problem might come from the fan itself: For quite some time I had problem with my laptop fan (running very noisely and too often, and somewhen as well wouldnt switch on at all with then the laptop overheating and switching itself off without warning). First I opened the laptop to reach the fan and cleaned out all the dust (with a hoover on slow speed and some cotton buds). That worked for a while until the fan seemed to have been died. At that time I not only removed the fan from the laptop for cleaning but opened as well the fan itself and somehow after several approaches it worked again but with a lot of noise. The final solution was to add some oil inside the fan (where the work mechanism is). Now it is running already several weeks after that without any further problem :-)