Try cleaning the cooling fan
My machine was at high temperature around 89 C when running a bunch of programs, after cleaning the cooling fan it dropped to 72 C , with smcfan control at 2/3 of the original speed. Quite a lot change with no major operation. Just wipe the cooling fan with cotton stick. I guess I am not going to take the computer apart checking the heat sink, with external cooling pad, it should be fine. Hope this will be helpful to you.