CPU overheating instantly - out of the blue

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Today I awoke to the sound of the CPU temp warning beeps from my PC. The CPU has not overheated since I replaced the stock heat sink with an oversized copper core heat sink tower over a year ago. The CPU usually runs at abut 120F but is triggering the alarm at 145F.

The fan on the heatsink is working although the bios shows no RPM speed for the fan (I'm not sure it ever showed this). I've changed nothing to cause this problem - the environment is not hot, no CPU intensive applications running, the heatsink feels cool but the CPU area does feel hot, plenty of case fans, with no other signs of excessive heat.

Can the thermal paste break-down over time? Because of space limitations it was next to impossible to install the heat sink tower - getting it to snap into place was very difficult and I don't look forward to doing it again to replace the thermal paste unless I have to (if that's necessary). It is unusable right now due to the fast overheating.

Is there a simple reason for this that I'm overlooking?
 
Yes some thermal paste does dry out, but your enemy may be dust at this point. Buy a can of air and blow the heatsink clean. Dumb question but I'm gonna ask anyway, is your processor heatsink fan spinning?
 
Yes, the fan appears to be operating normally. An inspection with a flashlight doesn't show much dust - at least that I can see. It overheats so quickly (within a minute the alarm is sounding) even just going into the bios. It's as if there is no heatsink. I'll try the compressed air right now.
 
the bios showing no rpm is a problem. The fan could be spinning slowly causing the overheating, however you can't tell since there is no rpm reading. I had remembered on my old AthlonXP system I had a temp reading program running in the background. All of a sudden it popped up a msg saying the RPM on my heatsink was very low. As soon as that happened I looked at my cpu temps and slowly it was rising. It went to about 80C then I shut it down. After I rebooted my fan rpm went back to normal. I guess it must of been a bug.

See if you can try another heatsink to rule out the RPM problem. Or if you can try looking at the fan itself, if you can actually see the fans spinning (depending on the size of the fan) it might be to slow (tho 120mm fans it might be possible to see them spinning since they have a slower RPM while an 80 or smaller mm fan you can not since they spin a lot quicker). But I recommend getting another heatsink or fan infact to replace the fan on top of your current hs.
 
I'm not sure that the bios ever showed an RPM for the CPU fan - but I agree it may be a problem although the fan appears to be spinning properly. The fact that the heat sink feels cool to the touch (even the tip of the copper core) seems unusual in an overheating situation.

I used compressed air revealing no dust to note, and have rebooted several times to re-check the temp.
 
Is it a particularly heavy heatsink perhaps?

Try putting your pc on its side just incase the weight of the heatsink is pulling itself away from your processor slightly.
 
The heat sink could pull off the processor if it was heavy enough and the fan could be kaput.

I've had similar problems years ago. I was using Artic Silver 5 as my thermal paste. I didn't read the instructions and applied a huge amount of the stuff onto my processor and then spread it around with a plastic bag and my finger. That worked OK at first until the air bubbles I massaged into the paste started to expand. The expanding bubbles pushed the paste around until it formed hi-points between my heat sink and processor and separated the two pieces with just small amounts of paste connecting them. Eventually I got the same temp warnings from my motherboard you are getting. The same thing can happen if you put the paste on the processor put the heat sink on and then take the heat sink back off and put it back on and don’t bother to clean the processor/heat sink and reapply more thermal paste.
 
I unscrewed my fan from the heatsink on my AMD 3500+ processor, and THATS where the dust was hiding! The processor was likewise sounding alarms after 1minute of activity, and now it operates at 30-40c! You've checked under the heatsink fan yeah?
 
Sounds like a solution in there someplace. The weight of the heatsink may be a factor - although it's mostly aluminum fins, it has a copper core and fan mounted on it.

I'll undertake the dreaded task of removing the heatsink, cleaning it, the fan, and the surface for a fresh application of thermal paste. In the initial installation of the heatsink it was next to impossible to place it properly - not much access to the clips that secure it.

It seems as though heat is not being transferred to the heatsink wheather due to separation caused by the weight or loss of transference caused by the thermal paste. The heatsink (including the tip of the copper core) were not hot to the touch initially, as I might have expected.

Thanks so much for the info, folks. I'll post results here.
 
I for two would like to know :)

I recommend you use Artic Silver Thermal Paste - its gotta be the best Thermal Paste out there and its easy to apply.

BTW, if you motherboard cannot find out the RPM - then the motherboard isnt monitoring the voltage going to the fan, therefore it cannot calculate the RPM. Make sure your connectors to fan are all ok.

Simon
 
Thanks for the recommendation PBNinja101. I've read a little about thermal paste today and would like to do it right - rather than often. I used some I picked-up at Radio Shack when I installed the heatsink initially.

The real problem is re-installing (re-seating) the heatsink without pulling it away (as Cinders described) while I try to attach the retaining clips, which I can't even see.

Thanks for the info.

IRT
 
It just may be worth the extra effort to pull the motherboard out of the case and attach the heat sink and then side it back in the case lock, stock and barrel if that's possible.
 
I hadn't thought of pulling the motherboard but that may be the one way to re-seat the heatsink properly...now I wish I had started with a full-size server case instead of a mid-size tower.

Need to give the mobo pull some thought until I get the thermal paste tomorrow. Thank God for laptops or I wouldn't be able to take advantage of all this great help here at Techspot!

Thanks again.
 
A thorough cleaning of the heatsink, fan, and contact surfaces with the CPU, a fresh application of silver thermal paste (about the size of 2/3 of a BB) without effect :dead:.

The temp reading in the BIOS climbs to 145 within seconds from a cold start. Can this processor really be heating-up this quickly or are the BIOS numbers wrong?

Definately nothing to do with the heatsink at this point. What could cause the CPU to heat-up so fast? Was functioning normally two days ago - back to square one today.
 
it may be that the processor has just broken some how and is heating itself up super fast

you could try taking the motherboard out of the pc and placing it on an anti-static bag with a desk fan pointing at it and see how how it thinks it is
 
I can't think of any other cause for the CPU overheating and am guessing a replacement processor is the next thing to try, unless someone can suggest another possible cause.

The current processor does not appear damaged or look/smell burnt.

Thanks again for all the responses.
 
It could just be a faulty sensor. Get everest home edition (via google) and speedfan (vis TS downloads) and see what they both say about the temperature.
 
I've got speedfan but haven't used everest before, but the CPU heat warning beep sounds long before the system loads and presumably would shut down at the predetermined temp (155F I think).

Can I disable the temp shutdown feature in bios - or if possible, too risky?
 
I can't advise you to do that. I will however say that the CPU has it's own thermal overload protection and should shut itself off to prevent damage.

But the decision to attempt anything like that has to be yours and yours alone.
 
Thanks! I thought I'd pick-up an AMD XP 2600+ processor to replace the XP 2100 currently installed (I'm told it should work with my system). Maybe try that first, although if it's a sensor, which seems to make more sense to me, it will probably show overheating even with a new CPU.

Thanks for the input rik.
 
I think it is more than likely a sensor problem. If that`s the case, then swapping cpu`s won`t do much good.

Most cpu`s have thermal protection built in and would automatically shut down before they fried themselves.

If it were my system, I`d disable the temp alarm etc in bios and boot into windows. I`d then run both speedfan and Everest as has been suggested and see what they say.

Regards Howard :)
 
Thanks, howard. That was my first inclination, just didn't know enough about it - thus, here I am at Techspot where the knowledge is!

Thanks again.
 
Obviously, there is always a risk with anything. However, there is no explanation for your problem other than a faulty sensor. Well, none that I can think of.

I`ve heard of faulty sensors on quite a number of occasions, so It`s not that unusual.

Regards Howard :)
 
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