T420 weird heat issue

[netrunner]

Hi,
I have tried to replace thermal paste on my T420 several times. It's equiped with i5-2540M, only iGPU, 2x4 GB RAM, dock + dual display. Everytime I do so, I test my laptop. Right after replacement or next day is all right, CPU temp doesn't climb over 83 °C under heavy load with fan level 7 (~4500 rpm). But during a week or so max temp grows up to 90 °C with fan level 64 (~5300 rpm) and CPU and GPU throttle. Everytime it's same workload, every night is laptop suspended and ~80 % of active time is very light load.

I've tried Arctic Silver 5 and Arctic MX4, both the same result. Also I've tried different approaches to apply thermal paste - one dot in the middle, thin film over whole cpu, several little dost... No luck. Room temp is almost the same.

Any ideas what can cause this? Thanks.

[RealBlackStuff]

Either your fan is not sitting properly on the CPU (most likely), or the fan is bad (possibly), or you have a bad CPU (less likely).
Take it off again, clean fan and CPU, apply thin AS5-layer over the whole CPU only, assemble, run for a few minutes, take fan off and check that the full AS5-layer is visible on the fan-plate.
If not, there's your problem.

[netrunner]

Weird thing is, that the temperature raises for a week. When I performed a test (at least two hours) right after replacing thermal paste, all was just fine. In case of not sitting fant it would overheat right away, wouldn't it? I can try to replace the paste once again, but I doubt it will help.

[RealBlackStuff]

Maybe someone else has another solution?

[hhhd1]

How do you stress test (when the temp is 83c) ?

I suggest you try using a recent version of Prime95, at the same time with Furmark, for proper stressing of the CPU+GPU.

[netrunner]

I use prime+furmark for ultimate stress test. For testing heavy load I use CS:GO - CPU usage ~70%, GPU usage ~95 %, which is a bit closer to normal life applications.