CPU overheats when tilting laptop !?!?!?

Hi there,

I got a Compal FL90, running a Core 2 Duo T8100.

The laptop runs fine, most of the time, but it tends to overheat sometimes (+100° C), and runs totally cool on other occasions (70° C) - both on full load, during runs with Prime95.

The fan is not the problem, it runs well, RPM increase with increase of temperature. Air flow is perfect as well, no dust or stuff like that. I even have the lid to the fan open, so this is not the source of the problem, I am 100% sure. I applied fresh thermal paste, so I am good there, too.

However, what I found out is that temps rise very fast (from 70° to 100°) in 25 seconds (under full load), when I tilt the laptop backwards. So, what I do, I grab it, lift it in the air, holding it. Then, I let the side where the LCD is go down, so that the keyboard is in an 45° to 90° angle.

When I tilt it the other direction, also 45° to 90°, temps get back to normal real fast - from 100° down to 80s in under 5 seconds ...

I use CoreTemp to meassure temperatures, Prime for getting the heat. I am running Vista, latest BIOS, all relevant drivers installed.

I am not familiar with heat sinks and stuff, but I think the copper pipes are filled with fluids. Can it be that the fluid in there dried out or something.

This would explain the change in temperatures, because when tilting it back, the remaining fluid would flow away from the CPU core, leading to far worse heat transfer. Tilting it the other way, the fluid would flow back to the CPU core, allowing for normal heat transfer.

Can that happen? If I am all wrong, who can tell me what this could be and what to do !?!?!?

Thanks in advance!

Cheers

 

Could be a poor wick in the heatpipe which isn't very effective at getting the coolant back to the hot end. Without gravity on its side then it'll be getting much less coolant.

 

Its possible that tilting the heatpipe will have an effect on the temps...however i don't think it will account for 30°

Have you checked the heatsink itself? Is it tightly on? If its loose, you tilting it could cause the the heatsink to lift up away from the CPU die leading to bad contact and a sharp rise in temps....all conjecture at this point

 

Nah, I am 100% sure that the heat sink sits perfectly. A friend of mine said, that it could be that the sensor is maybe to on the CPU but somewhere else on the motherboard. So the tilting could de/in-crease airflow there, leading to "wrong" readings.

Any other ideas are very welcome.

Cheers

 

beat me to it makes me wonder if the heat pipe has gone bad. Heat pipes DO go bad. when heat pipe go bad they can do really weird usually the cpu gets hot and the heat sink stays cool. that stuff in the heat is actually supposed to move at near super sonic speeds or so i've heard.

 

If you could give us a screenshot then we could tell you what sensor you're reading. If you're using the actual CPU sensor then oriantation will not effect the readin since it's embedded in the chip.

 

hmm never noticed this with my fl92 t9300 and i often used it on a tilted angle (right on bed left raised and slightly back on thigh). not a gamer but i do often watch movies, re-encode movies from my camera, copy and burn dvd movies in this position my cpu temps never got past 60. the 8600m whole different story 75c idle

 

How can heat move at 'near super sonic speeds'? lol...

Never heard of this before - any links?

 

Well it's not simply heat which is moving through a material, it's physically being carried. Although I doubt it would move at supersonic speeds I can well believe that the vapours are moving pretty quickly inside.

 

Nah,

10Char.

 

my boss was reading some Wikipedia and some other sources on the net, i agree probably not that fast but, still move fairly fast in the gas form.

 

Thanks everyone.

I also have/had several FL90 before (for repairing), and I never saw something like that ...

As there is no obvious fix other than trying a new heat sink, I might just do that.

Thanks again all!

Cheers

 

the only other thing i could think of is some how some loose object is making some freak short on the MB level causing the temps and stuff ti weird out either software or physically.

 

May be victim of a gravity driven heat pipe system. Fluid evaporates inside when it gets hot and goes into gas form and raises into the heatsink area to cool into liquid.

The liquid is pulled down by gravity and ends up back at the heat source where it started and cools the heating element and the cycle starts all over again.

Most modern heat exchange systems are designed in a way to work in more than orientation however not all of them are...

 

Petty sure a lot more FL90 users would be pissed if that were the case. My guess is a heatsink defect, as others have mentioned. Maybe it's leaking the vapor a bit.

 

Technically, shouldn't a heatpipe work due to capillary action and pressure more than gravity? The phase change and resulting pressure change should be enough to drive the vapor towards the cool end where it condensates then flow back towards the hot end in liquid form. The small form factor also helps with that kind of motion.

It's been quite a while since i did thermodynamics though so i could be wrong. A poorly designed/defective heatpipe could be influenced by gravity though which might indeed be the OPs case.

 

If you have a decent wick then gravity isn't usually an issue but with a poor wick it can have an effect. There are cases where people have used GPU coolers designed for a standard ATX case in a rotated case (eg RV02) and it hasn't worked optimally because the coolant isn't being returned effectively.

While on a desktop it's usually fairly safe to say that it's going to be operating in one speicific orientation (so poorly wicked heat pipes aren't much of an issue), laptops are expected to move about.

 

It is by design - I tried with two more Compal FL90s, all showing the same behaviour.

Tilting in backwards makes it climb to 100° an above, leveling makes the temps drop back to normal.

I do not know if it is related to the sensor, the software or if the heat transfer really gets that much worse - nevermind.

Just don't tilt your laptop while running Prime95, hehe.

Thanks all

Cheers

 

Thats F'd up!!!

 

Yes. Could have told you for sure this was the case if I had seen it earlier.
Older MSI laptops are the same.

There is potentially a way to make them more effective on the side which I don't recommend. Take a pair of pliers and smash the heatpipes to make them less rounded, more square or even star shaped.
This is how very small experimental heatpipes work. The inside of the pipe basically works as a wick itself.

Why exactly?

Optical drives, HDDs etc do not run as efficiently on their sides.

Must we avoid all reminders that all electronics have a basis in mechanics and physics?

Of course, if anyone has some sort of a disability and actually needs to use their laptop on its side, you have my apologies.

 

hahaha. In all honesty not all laptops have this problem, so it's not really acceptable to me for any laptop to have the problem, or at the least there could be a fix. hard drives have come a long ways. i guess, i could under stand HDDs not working as well on their side but, i have never seen that cause problems not, at least with newer drives. same with heat pipes now if it is among some of the earliest laptop heat pipes then yeah okay makes since.