Cold CPU overheating

DevPete · 31 Mar 2024 at 20:14

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

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.

Removed User 345456 · 31 Mar 2024 at 20:50

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?

DevPete · 31 Mar 2024 at 21:18

keef247 said:
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.

doyll · 1 Apr 2024 at 23:35

As stated, get some new TIM, then remove, clean, apply new time and re-seat. Please let us know how it goes.

JasonM · 2 Apr 2024 at 17:03

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.

doyll · 2 Apr 2024 at 18:07

What Jason said.

DevPete · 2 Apr 2024 at 18:31

JasonM said:
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.

Armageus · 2 Apr 2024 at 18:41

Should it be Tim? A lot of laptops use thermal pads as tim normally isn't enough to bridge gaps to the specifically designed coolers

Drumroll · 2 Apr 2024 at 19:27

Every laptop I have opened before all used thermal paste, never had the bad luck of using thermalpad. Always have some good thermal pad at hand, just in case, but I haven’t opened loads of them. Must be 20 or less, mainly Dell and HP, and some old Sony.
For laptops, as it will run hotter than a PC under similar scenarios, a thicker thermal paste is recommended. Something like the Arctic MX4 or MX6 should be good. Other better performing ones may pump out within months at best.

doyll · 2 Apr 2024 at 22:13

Heatpipe coolers don't get hot. The hottest area is about middle of finpack where the vapor is condensing into wicking on inside of heatpipe. Then the liquid wicks to cooler base on CPU where it boils into vapor and move thru heat into fins and condenses again into wick.

Thermal pads usually don't more heat away from heat source (CPU) as good as a good TIM seat. Key is CPU is tight metal to metal contact to cooler base with a very thin film of TIM filling microscopic voids in crystalline structure of meta.

Aluminum is 190 W/m-k,

Copper is around 400 W/m-k.

TIM is 5-15 W/m k.

Air is 25.9 mW/m k.

1W/m k is 1000mW/m k

DevPete · 6 Apr 2024 at 19:42

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 · 6 Apr 2024 at 20:33

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.