Cold CPU overheating

[DevPete]

The title sounds strange, and that's why I'm asking on here

I'm looking at an i3 laptop (approx 3 year's old I think), which appears to be overheating. It has typical symptoms such as screaming fans, blue screens and then it refuses to do anything other than display the power LED (blank screen etc.). I can't monitor temperatures etc. as I only managed to login once for a brief moment. The login screen gets the fan spinning, and a login takes the fans to max.

My understanding is that is has always been noisy (from new) but has recently had the problem where 'the screen won't come on'. A computer shop tried fixing it once, but it didn't help. The laptop belongs to a family member, which is why I don't know the full history.

I've looked inside and it's almost spotless (no dust), and the thermal compound looked pretty good. When it crashed recently, the heatsink/heatpipe near the CPU was only around 35C, and where the fan is, it was less than 25C as the heat hadn't even got that far.

I'm thinking that there is either an issue with the thermal compound or the CPU is running really hot . I was going to replace the thermal compound but my compound appears to be too old, so I would need to order some more, but I don't know whether it's worth spending money on it. The CPU is only 15W TDP, so I'm really curious about this. Any ideas what could be causing this or how to fix it? I've seen some videos online, which show that the heatsink needs replacing, but as the temperature is so low, I wouldn't expect this to be the problem.

 

[DevPete]

Did you not change the thermal paste when you removed the cooler to look at it? Definitely should have if you disturb it, and always worth doing when you have the opportunity anyway...
Could be a crushed heatpipe somewhere from the previous repair?

I am planning to replace the thermal paste, but I need to get some ordered.

 

[DevPete]

CPU / GPU coolers you want them to get hot, hot is good as it means thermal transfer is happening.

If the coolers are not getting hot or even warm at idle, then thermal transfer is not occurring correctly. The result is the cooling fan can't work efficiently, so the fan runs at higher RPM to compensate.

That's what I thought. Lets hope that the TIM fixes it , although the previous compound looked fine. TIM is in the post.

 

[DevPete]

I've changed the thermal paste and I think it's better but I'm still not sure that it's right. It seems to be lasting longer now and it hasn't failed yet. The CPU is at 100%, which appears to be for updates etc. I'm planning to boot it for short periods at a time until the CPU idles. Once it's idling, I can install a temperature monitor and gradually build up the load.

The fins on the heatpipe still don't get very hot (hit around 26C IIRC), but the CPU end was over 40C, so I think the paste is doing the job. I'm wondering whether there is a crack in the heat pipe or whether it's ok now and just runs loud. I guess that fan could be making the fins cool.

 

[DevPete]

It seems to be fixed. It turns out that the heat pipe is working correctly. I was just being a bit stupid with measuring the temperature. My thermal camera can't see the temperature of the copper, so it worked where the label was, but not on the fins. I found this out by touching it and getting a surprise

The CPU temperatures peaked at 83C, which is higher than I would have liked, but not enough for it to fail. I have doubts about how it will perform on a hot day with a 30+C room temperature, but I guess this is how it's designed to run.