Thinkpads Forum

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.

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.

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.

Maybe someone else has another solution?

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.

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.