I opened my old trusty Mac Book Pro “Gravitas, what gravitas?” (late 2012 10,1 retina 15″) to upgrade its SSD to 1TB. It was running very noisy for a long time, and accidentally I discovered the reason! The fins of the cooling grid connecting to fans were almost totally blocked by dust balls (see upper right)! I wonder how I will be able to fix this in the new mac books where everything is glued.
Btw: Be very careful with the screws! I lost one, because it skipped a thread without noticing it, and Aluminum threads were destroyed. The instructions to upgrade the SSD are here. Probably I should’ve followed the order they install the screws back.