Replace the thermal grease/paste

There is no guide yet on how to replace the thermal grease/paste.

These Macbooks are now around 4-5 years so it's not a bad idea to replace the thermal paste.

They're not obsolute so there will still be users who can benefit from a guide.

Update:

So I was able to open the MacBook and disassemble the motherboard with the video.

Since I'm comfortable around electronics (this isn't my first time opening up a MacBook, laptop, or even a smartphone), I did choose to replace the thermal paste on the cpu and gpu.

And honestly, after four years of service... Kind of disappointed about the original paste. Dan said that paste will last longer now due to improvements, but the original paste was crumbly as hell. Furthermore I noticed small blank spots on the cpu and it's heatsink, so not very good spread. The gpu did have a good spread. They definitely were generous with the paste on the gpu, because its surroundings were covered with paste too.

Cleaning wasn't difficult, as I said the paste was in a very crumbly state.

After cleaning I gave the copper plates of the heatsink and the cpu and gpu some time to evaporate the alcohol.

I used Noctua NT-H2 and used the "X" to spread the paste on both cpu and gpu.

The only annoying experience was to place back the motherboard in the case. I needed multiple attempts because there was always some small connector/ribbon cable underneath the motherboard. Ugh! After playing like an octopus for a while, I was able to place the motherboard back and with all connectors/ribbon cables out on top of it.

It's do-able but only for people who have a steady hand and... most of all... lots and lots of patience. Take your time. Take some breaks if you get tired or frustrated because the moment that you attempt to work a bit faster or anything like that... something will go wrong. I 100% guarantee that.

I made only one mistake. The connector cable from the left fan is incredibely fragile due to its L-shape (that's what I think). In trying to get the L-shape cable from underneath the board to the top on the board, I got a small tear in the ribbon cable. This fan no longer works. We learn from our mistakes. Should've taped the connector on top of the fan, I wouldn't had an issue to "fish" for the cable since it can't get trapped underneath the board that way. Already ordered a replacement fan.

The temperatures are amazing though. In idle I went from 60-63° to 46-51°. The one remaining fan is also a lot quieter. I'm not going to claim this huge difference to the new paste though. There was so much built up dust in the MacBook... I was genuinely surprised that the MacBook didn't have much higher temps in idle. Both fans were completly covered up in thick dust, and the outlets on both fans same thing. How it managed to get some kind of airflow through those thick dust is a mystery to me.

Anyway, I am very happy with the result. Yes, I did damage one fan connector, but one can only learn with making mishaps.