CPU Temperature Question

My system uses an Intel Core i5-2500K Sandy Bridge 3.3GHz  6MB Cache, LGA 1155 processor.  A few days ago I saw a popup from the system tray, warning me that the CPU temp had reached 70 degrees C.   I opened the case and found that the Intel CPU cooling fan was full of dust and debris.  I replaced the cooling device, adding some thermal grease.  After a reboot, the CPU temp in Bios was reported a 47-48 C.  Today, the popup warning about 70 C happened again.  Using a Windows application called RealTemp, the CPU temp was reported as 68-69 C.  However, terminating a Windows process, which uses a lot of resources, reduced the temp to 40 C.   I have run this process hundreds of times over the years without a CPU temperature warning.  Wondering what I must do?
ddantesAsked:
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JohnBusiness Consultant (Owner)Commented:
Checking cooling and the suggestions here is a good idea.

But a process running non-stop forever at 80% CPU will heat up any CPU and you know by killing the process that the CPU cools down.
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andreasSystem AdminCommented:
clean cpu carefully of any remains of old cooling compound. consider a larger heatsink. Ive also observed that older cpus need bigger heatsinks. maybe the heatspreaders contact to the chip itself will become old too and the heat couldnd sperad as good as before to the metallic surface of the CPU.
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andreasSystem AdminCommented:
Hmm sandy bridge still uses solder to connect heatspreader and chip so it should not degrade over time as on newer CPUs which uses thermal compound.

So Im guessing you need to carefully clean your cpu and bottom of heatsink from any compound remains than clean from dust and particles. and than re apply a new very thin layer of compound and reattach the heatsink.

Did you also change the electrical fan alongside the sink? maybe the fan does not perform as well as before.

Did you install some updates of BIOS or other software that could affect CPU fan speed controls? MAybe its a software issue.
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Michael-BestCommented:
" I replaced the cooling device, adding some thermal grease"
Too much or too little and also the quality of the thermal grease can cause this.

Suggest you read tomshardware.com:
"Thermal Paste Comparison"

Link:
http://www.tomshardware.com/reviews/thermal-paste-heat-sink-heat-spreader,3600.html
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ddantesAuthor Commented:
Thanks to both experts for comments.  I replaced both the heat sink and fan, which are integrated.  The replacement is the same model as the one which performed adequately previous to this issue.  I did remove all traces of old thermal grease from the CPU, and there was no old grease on the new cooling device.  I used the same thermal compound, in the same amount (a lentil-sized blob), which had worked previously.  I did flash update the BIOS today, but the issue originally developed before the BIOS update.  Bios reports the CPU fan speed as ~1872 RPM.
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JohnBusiness Consultant (Owner)Commented:
However, terminating a Windows process, which uses a lot of resources, reduced the temp to 40 C.

What process? The vast majority of processes will use less than 5% CPU more than 95% of the time and should not heat up a CPU. That metric has worked for me for decades.

Please let us know the process and a screen shot of Task Manager with CPU usage sorted to the top.

Thanks.
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ddantesAuthor Commented:
The process is O&O DiskImage, which I have used for almost ten years.  I never bothered checking CPU temperature while running this, nor did I get any alert popup about it before.  The highest temp during this process, so far, is 85C.

Task ManagerRealTemp
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JohnBusiness Consultant (Owner)Commented:
That is backup software and you can see your other processes use very little CPU. Can you unload this and only run when needed?
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JohnBusiness Consultant (Owner)Commented:
The other thing to check would be the backup parameters. It may be going nuts trying to deal with busy files.
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ddantesAuthor Commented:
I only run this program once a week, and it takes a couple of hours.  I was able to change the CPU priority to "low" instead of "normal", but that hasn't made much difference in the CPU load or the core temp.]

If the temp runs ~ 80 C during peak load, is that still acceptable?
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KorbusCommented:
Don't ignore your other fans.  It's the ones that suck air from outside of the case that usually get caked with dust, well before my CPU fan.  If those case fans are not blowing enough air, even if your CPU fan is good, there wont be enough cool air in the case for it to work.
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JohnBusiness Consultant (Owner)Commented:
I think a temperature over 70 is too high for prolonged use.

Backup is disk activity and even for a 2 hour run will not heat up like that.

Maybe uninstall the software, restart and set it up again.
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ddantesAuthor Commented:
OK, I'll try that and post again.   The software makes a snapshot of the drive at the start of the backup, so it doesn't matter whether files are in use during the process.

I did clean out the other fans, and replaced the chassis fan, when the issue first developed a few days ago.
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Michael-BestCommented:
For any CPU ... 78 C is way too hot and will lead to the PC to  freeze  (hmm a strange term for an overheating CPU) but non the less overheating can and will cause your system to freeze ( stop working may be a better term?)

Read:
http://www.buildcomputers.net/cpu-temperature.html
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rindiCommented:
If the fan is full of dust, it usually is enough to clean out the dust, you normally don't need to change the complete heatsink because of that. Also when you reattach the heatsink to the system, it is very important that you reattach it properly and firmly, If it isn't attached properly, it is possible that the heatsink and the CPU don't make contact with each other optimally, and that would greatly reduce the heatsink's functionality. So make sure that it is properly and firmly attached. Also, as has been mentioned above, make sure you only use a very small drop of thermal transfer paste. Too much can cause more heat insulation that dissipation.

Another thing to check is your BIOS settings. Many have options in there to control the fan speed. maybe you just have to increase that speed. Also check your BIOS version. If you have a buggy version it might cause fan speeds to be too low, or the temperature readout might be erratic. If there is a BIOS upgrade that addresses such issues, it can help to do the upgrade.
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ddantesAuthor Commented:
I only changed the complete heatsink because cleaning it didn't appear to correct the problem.  Based on other Expert comments, I uninstalled and reinstalled the software, and also tried an earlier version of the software, but the disproportionate CPU usage and overheating continues to happen when the application is running.
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ddantesAuthor Commented:
I just tried a different disk imaging application, R-Drive Image.   TaskMgr reports CPU utilization up to 65%, and the CPU temp gets as high as 74 C.    My computer has always run very slowly during disk imaging, and perhaps the high resource consumption and elevated CPU temperature have always been excessive.  I never got a warning popup about the temperature before, but it may be a chronic problem.
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JohnBusiness Consultant (Owner)Commented:
The imaging program may have some issue with the operating system especially since you say this has likely been a chronic problem.

There could be so many things at this point, you may wish to consider backing up and reinstalling Windows.

However, this is the system you want to upgrade to Windows 8, so perhaps uninstall the imaging software and wait until you back up and install Windows 8.
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ddantesAuthor Commented:
I will look for another disk imaging solution which may be less troublesome.  Over the years, disk images have saved me from a world of hurt, innumerable times, so I'm not inclined to abandon the practice of saving an image every week.

Meanwhile, I tried something with the Setup utility on another computer with the same Asus P8H67-M PRO/CSM motherboard:  BIOS>HW Monitor>CPU Q-Fan Function set to Enabled>CPU Q-Fan Mode to Turbo.  After exiting BIOS, the CPU fan speed increased from ~1900 to ~2300 RPM.  When the current processes are finished on this system, I'll try making the same adjustment, and hope it shaves a little off the CPU temp.
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ddantesAuthor Commented:
I appreciate all Experts' suggestions.  The issue seems related to a specific application which is consuming excessive resources and overheating the CPU.  I'll need to find an alternative application.   When that disk imaging software isn't running, the CPU temp is in the 40's C.
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andreasSystem AdminCommented:
But nevertheless a proper cooling system should be able to cool down the PC to a level that even full load of all components will not lead to overheating.

Where your PC is located? and how warm is it inside your room?
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ddantesAuthor Commented:
The PC is located on the floor of my home office.  The room is warm, as we live in Hawaii.  Ambient temperature ranges from low 60's to the high 80's F.  The office is air conditioned.
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andreasSystem AdminCommented:
High 80s for PC environment temperature is quite high. So is the cooling problem only appearing when the office is warmer than 25°C? (77°F). Where the PC pulls in fresh air? is the inlet dust free? some cases have air inlet filters from foam, maybe those foam mats are totally blocked by dust.
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ddantesAuthor Commented:
The inlet ports on the case are perforated aluminum, and they are now free of debris.  There is no foam.  I can't say whether the cooling problem only occurs when the room is warm, because I have just become aware of it, and it seems to occur only when running an application which uses a very large amount of CPU.
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andreasSystem AdminCommented:
try again with high CPU load when the room is cool. usually the fans inside can only LOWER the temperature a certain amount of degrees. if outside temp is higher then the resulting end temperature inside the PC is higher as well.

Than only a bigger heatsink and stronger Case/CPU Fans can lower the temperature more.

To try just adjust AC to cool room to 20°C and test again (if you can set the AC yourself).
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JohnBusiness Consultant (Owner)Commented:
@ddantes  - Thanks for the updates and I was happy to help.
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