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ASUS G531GW: noticeably higher GPU temperatures after repasting

Level 8
Hi everyone!

So I decided to change thermal paste in my ASUS ROG Strix SCAR III (model № G531GW, i7 9750H + RTX 2070, 16 GB RAM), as the last repasting was done by an Authorized Service ~14 months ago during the faulty cooling fan replacement.
Did some research by reading forums, watching some YT videos on the topic, and decided to go with Arctic MX4 as it was universally loved and recommended by a lot of people who own this exact laptop model and other fairly hot ASUS ROG laptops.

I had some doubts about what to do with the thermal goo put by ASUS on video memory chips and VRM elements, as you obviously can't buy that exact stuff ASUS used during the manufacturing proccess. Some people advised to clean the goo off and use the same thermal paste as on CPU and GPU crystals. Fewer people were in favor of replacing the goo with thermal pads, but the recommended thickness of the pads was really controversial topic.

When I disassembled my laptop, I saw that the thermal goo was pretty dry and didn't really cover the surface of video memory chips and VRM elements evenly, there were uneven clumps of it on some chips, some of them were completely clean, and the overall 'plasticity' of the goo didn't let me to reapply it evenly (I honestly tried). Then I decided to clean it off and to use thermal paste instead as was recommended by some folks on the web. I didn't know how thick the layer of paste should be where the goo were previously, so I went with the same fairly thin layer as on GPU and CPU crystals.

After assembling my laptop and switching it on I noticed an improvement in CPU temperatures right away. Before the repasting it was 55-60° С in idle in Silent mode (the one in Armoury Crate), after the repasting it was 48-52° in the same conditions.
But as soon as I tested it in games, I noticed a problem with GPU temperatures. Before the repasting, GPU was never hotter than 76-77° C under the max load (e.g. Cyberpunk 2077 with RTX lightning 'on' utilizes 97-99% of GPU resources according to GeForce experience overlay, and I could play it for unlimited amount of time with GPU temps staying at 76-77° C). After the repasting, GPU now gets so hot that it easily reaches 86° C in a couple of minutes in game (Cyberpunk 2077, Battlefield 3) and that is the moment it starts to throttle, reducing the FPS for a couple of seconds to drop the temps of GPU to 80° C, and then it goes up to 86° C and throttles again, the cycle never ends as long as any 3D game is running.
For 2.5 years of owning this laptop I never encountered GPU thermal throttling, so it definitely is a consequence of the repasting.

Now, the question is what exactly did I do wrong and how can I fix it? I definitely tighten all the screws of the heatsink evenly and firmly (but not too tightly), I cleaned all the dust and lint from the cooling system, the cooling fans are working as well as they did before the repasting.

My guess is that it's thermal paste applied instead of thermal goo on the video memory chips causes this problem (there is no separate sensor for video memory in this laptop AFAIK, so the GPU temps sensor probably shows avg of GPU and video memory temperatures, but correct me if I'm wrong about it).
Maybe I should have had a thicker layer of paste where the goo was? But how thick should it be? Maybe I should try some other paste? Or maybe I should buy thermal pads (again, how thick should they be?) and use them instead? Or maybe MX4 is just not that effective for the RTX 2070?

I'm not sure about anything anymore, so maybe someone had the same experience and knows how to solve this issue?

Thanks in advance.

swap the thermal pads to thermal putty to get better compression
what i did when i reapplied LM to my zeph was apply the putty, then attach the heatsink and push it down to squish the putty in place, then screw it in and push down more.


then i unscrewed the lot and applied the LM and PTM then reapply heatsink

so i could get proper contact

Thanks, I'll try that.

Level 8

The last update: the problem is kinda solved. 
I opened up the laptop yesterday to see if the contact between GPU and heatsink is good, and the contact was bad once again: 


My guess was that because the surface of heatsink that contacts VRAM (silver plate with a lot of big blue piles of putty on the photo above) is not leveled with the surface which contacts GPU itself and is closer to motherboard when installed, the GPU had no proper contact with heatsink on that side of crystal because that side of heatsink kind of 'hanged' in the air because of the thickness of solid thermal pads (last year) and the amount of thermal putty I put on VRAM a few weeks ago.

So what I did is took some of the excess thermal putty off of VRAM chips surface, spread the rest evenly so the layer wouldn't be > 0.5 mm (because I know for sure that 0.5 mm and thicker prevents GPU from contacting the heatsink properly as I applied 0.5 mm solid thermal pads last year) after the final pressure is applied, then put some fresh thermal paste on GPU and CPU, put the heatsink in its place without screwing it in and applied gentle pressure, then lifted it up to see if the contact with GPU and CPU is good, which it was. So I finally put the laptop together and ran some tests.

As a result, the temperatures of GPU dropped 5-6° C after this 'procedure'. The new temperatures are in somewhat comfort zone for me personally, although they are not the same as they were when the laptop was new and untouched.
I'm sure that if I experimented with the thickness of thermal putty layer more, I could get these temperatures even lower, not to mention the possibility of applying liquid metal (which I won't do, the risk is not worth it for me) and using different (better) thermal paste in GPU and CPU to help with a heat spread even more.

tl;dr: the problem was in bad GPU-to-heatsink contact. A very low amount of thermal putty should be applied to VRAM chips and VRM elements just so that after installing its thickness would be ~ 0.2-0.3 mm. That way the heatsink would sit properly and all surfaces would have a great contact. 

Thanks for all the help and advices, guys.