Probook 4520 CPU Overheating??

I have a well used Probook that occasionally shut down. It is now worse and will shut down immediately after booting. I have cleaned the fan (not dirty) and replaced thermal paste to no effect.

On startup, the CPU heat sink gets too hot to touch within two seconds, so I am suspecting a component failure.

Is there a fix or do I just toss the machine?
Martin EversAsked:
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i fear there's not much you can do, other than replace cpu (5%) or motherboard (95%)
look if it's still got warranty
Martin EversAuthor Commented:
Thanks nobus. I removed the heat sink, applied new paste, left the panels loose and so far, it's holding up. I installed CoreTemp which tells me that both cores are at around 50C - within spec. If it's still fine after three hours, I'll screw the panels back - but I still suspect there's another problem. The back fascia and bottom of the case are distorted from extended overheating.
Thanks again.
RaminTechnical AdvisorCommented:
Dust can short Electrical circuits and can cause such a problems.
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Dr. KlahnPrincipal Software EngineerCommented:
Check the fan for function and speed.  The fans used in laptops typically use el cheapo "rifle" bearings, which means no bearings at all.  When the lubricant gums up, the fan slows down and eventually freezes.  A new fan is worth the investment as it will only cost a few bucks off fleabay.

Clean the fan blades.  They tend to pick up dust and hair on the leading edges, which unbalances the fan and causes wear on the bearing.

Also carefully inspect the case vents for dust and hair.  Vents can look clean out the outside but on the inside be quite clogged.  Anything less than full-bore air movement will cause a laptop to overheat.  If you find a dust plug, pick it out with dental picks.  Don't attempt to blow it out with canned air - that often causes more problems than it cures.

In systems that use heat pipes with internal-grid heat exchangers make sure that the heat exchangers are clear and air can flow through unimpeded.

In a difficult case on an older system used in a fixed location I sawed the grilles out of the vents to provide more air movement, but this also has the undesirable effect of letting everything into the system that comes by, including ants, roaches and dust mites.
>>  left the panels loose  << ????  what panels?
i never found the fan blades the big problem, but the dust buildup in the radiator outlet to the outside
Martin EversAuthor Commented:
nobus - the fan cover, keyboard and rear fascia are  the panels concerned. I can see the fan spinning and feel the temperature gradient down the copper strip. The machine has been running for four hours. If it is still running tomorrow  I'll re-attach the fan cover and re-monitor.

Dr. Klahn - thanks for the comment. The duct, grille and fan were all largely free of dust.

Ramin - there was very little dust.

This appears to be one of those 'WTF?' problems appearing terminally resistant one moment and easily resolved the next - in this case surprisingly by a repeated application of paste.

Thanks again all you guys. I'll post a final sign-off tomorrow.
could be the old heat paste dryed out- or the heatsink was moved  -giving little cooling
Martin EversAuthor Commented:
Yep. The underside of the case is bowed out and the rear fascia strip is warped from extended overheating. There wasn't too much paste - the whole computer is now operating at room temperature.
well - if it got that far - i think you're Lucky it still works at all
>>   There wasn't too much paste  <<   should only be a small drop
Martin EversAuthor Commented:
Just to wrap this up, apart from looking like the 'computer that Jack built' it is currently all at room temperature.
However, I am unsure of the purpose of the metal cover. It will get hot from convection from the copper heat rod which is within a couple of millimetres, but there is little or no way for that heat to dissipate through a metal-to-metal contact so it sits there warming up the keyboard and generally radiating its heat load. As a quick 'n dirty treatment I have placed a blob of thermal paste between it and the fan housing. Might make a difference.
Anyway, thanks for all your help guys.
what ere we supposed to see on that pic??
Martin EversAuthor Commented:
Sorry - the white spot of thermal paste (now circled) connecting the fan cover to the fan housing.
i doubt if that will have a noticeable  influence on the temps
but since it's running ok now - enjoy !

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When the heat sink was removed were all the thermal pads removed and replaced with heat sink compound?
Martin EversAuthor Commented:
Yup - cleaned and spotted. Half the original paste had disappeared which makes me think that part of annual or biannual scheduled maintenance might be paste replacement rather than wait until there is the smell of overly hot electronics.
I suppose the saving grace the ease in which the Probook can be maintained.
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