Intel 8700k suddenly one core hotter than all the rest

[Vivid Dream]

My i7 8700k is delidded with LM & has been comfortably running on 5.2 GHz 1.38v with temps of up to 65 degrees Celsius benching a score of 1670 on Cinebench R15 for a little over a year now. I did a random temp test using realtemp & Coretemp recently (after watching a de8auer YouTube video) while running Cinebench R15 & my core 3 temp spiked to 100 degrees while all other cores remained at 65 and lower & my pc locked up and I had to force shutdown. Then I restarted & ran it again & the same thing. I suspected maybe it was the thermal paste, so I cleaned it up, reapplied paste & reseated, but still exactly the same temps. The 100 degrees Celsius spike on core 3 happens instantly as soon as I hit Run on cinebench, before the fans have a chance to increase RPM, so I'm guessing it's the temp inside the package heating up so darn fast. So after that I then bought a new cooler, Noctua NH-D15. No change in temps across the board. My cooling us more than adequate, though for some reason all of a sudden my core 3 has decided to run extremely hot. Like 30+ degrees hotter than the other cores. 

I updated my bios to the latest version & no change occurs. I tried tinkering with my overclock & I discovered that the more volts I give the vcore the higher the temps on core 3 become, but the rest stay the same... Why does it seem like my core 3 is receiving more volts than the other 5 cores?

 

Is it possible for the LM to shift position on the die underneath the IHS? I believe LM doesn't degrade within 1 year... Do sensors become faulty randomly? Does the TIM degrade over time? 

 

If no other solution comes to mind, I will delid & relid again & replace new LM to the die, though if that doesn't work I am absolutely beyond ideas... 

 

Any thoughts?

 

I'm running:

Gigabyte Aorus Z370 Gaming 7 rev 1.0

i7 8700k

G.skill Trident Z 3600mhz 2x8gb (dual channel)

Seasonic Prime Ultra Titanium PSU

Noctua NH-D15

[manikyath]

my guess would be either mounting pressure on the liquid metal, or that it 'leaked' away slightly. as the name implies, 'liquid metal' is well.. liquid.

[Vivid Dream]

3:11AM atm & no LM left. I'll order some tomorrow & relid when it arrives & let you know what happens

 

[Falkentyne]

3:11 am (two hours ago?)  That would make it 5:11 am now.  Where are you from?  China or HK or philippines?

Anyway, you need to take the IHS underside and CPU and sand it with 1500 grit sandpaper.  Just use your fingers.  That will get any hardened leftover residue removed.  You don't want a mirror finish or a reflective layer because LM adheres very poorly to a smooth surface.  So use the 1500 grit until all the old residue is removed.  It will be obvious when the residue is removed from the CPU, but sometimes tiny bumps stick that have to be sanded off.

 

The IHS takes a lot more work unfortunately.

 

Then use alcohol 91% and some paper towels to fully clean it, then after that, use a lint free cloth to make the surfaces pristine.  Make sure there is a dull finish on both.

Always make 100% SURE all of the "silicone adhesive" from the original seal is fully and totally removed.

Then apply new LM on the CPU and spread it.  You will see it will spread very easily since the CPU die is now dulled out.  Then apply a matching layer under the IHS.  Then reseal.

You can use the four tiny drops of RTV Silicone (DO NOT use superglue) in each corner of the IHS for a reseal, or--you can use a floating IHS.  For floating IHS, my method is to apply 4 dabs of Kryonaut or another normal paste on each corner of the IHS!  This will give extra resistance to the IHS moving around (it makes a huge difference!) when you go to relatch it into the socket.  It's much better than not having -anything- there at all.

 

Your temps should be spendid after.