Chosen Solution
Hi, So, my MacBook Pro has had this issue for a good while. I just picked it up again after 4 months of collecting dust, to see if its possible to fix it. We´ve tried changing the heatsink without results. Or at least positive results. I can be surfing in safari or playing CIV V which is the hardest thing this machine has ever done - and it suddenly shuts down without warning. I tried stresstesting it today both CPU and RAM and nothing happened, until the stresstest was finished, then it shut down. And then i can start the MacBook again, and it shuts down after a minute, or it can take an hour. I´m kinda lost here, all help or propositions will be appreciated. It is a 2.5GHz with 16GB and 256GB SSD Update (04/27/2018) So, I sent it to Apple. They switched out the motherboard(In February), and it hasn’t crashed once since! Yay!
Did you reapply new thermal paste? if you remove the heatsink you must clean off the old thermal paste and reapply new thermal paste. How to Apply Thermal Paste MacBook Pro 15" Retina Display Mid 2014 Heat Sink Replacement
I had this problem with my mid-2014 15” mbp. Mine would pretty reliably shut down soon after opening a browser. If I opened nothing, or just copied files, it might go 30 minutes before shutting down. First screen would go black, then it would turn off after about 5 seconds. I reset NVRAM and SMC, no help. I did a clean install of OS X. No help. I had already replaced the topcase/battery on this machine a while back. This machine has seen extremely heavy use for the about 5 years I’ve owned it. So because one of my fans would make a lot of noise under load (had been going on for months) I had already ordered 2 new fans. Was just procrastinating replacing those. So I replaced the old and very dusty fans and at the same time replaced the very old and crumbly thermal paste. Removed all the random dust bunnies from the inside. Put it all back together. Fixed!
