CPU performing temperature weirdness (one core temp spikes)

[Impatient Traveler]

Hello there, I could use some advice on what might be wrong with my i7-8700K CPU.

 

Quick story, I bought the CPU something like two years ago used. It had the thermal paste replaced with liquid metal by the original owner (had it done by someone who does delids professionally) and supposedly held 5GHz easily on a custom water loop with very good temps. Due to life things (c) I couldn't get a motherboard that would let me actually install it until last week. 

Upon installing it I noticed weird behavior of the cooler, with it constantly speeding up and slowing back down, 3 seconds full speed, 3 seconds slow, and so on. It doesn't do it all the time but nearly so.

I've been monitoring the temps in CPUID HWMonitor and most temps are looking great. The mobo's CPU sensor is chilling at 35ish C and slowly ramps up to 50ish under load. Same with cores 0, 2, 3, 4 and 5. Meanwhile, core 1 and "package" idle at 45 or so, but as soon as any load is placed on the CPU they'll start rapidly spiking to 100C and back down. Now I'm talking about those spikes taking place over ONE(!) refresh inside HWMonitor. It will read 47, then 100, then 47 again with less than a second between the read-outs.

The 100C events absolutely do throttle the heck out of the CPU, so whenever something's happening I'm stuck with the CPU trying to speed up and slow back down at breakneck speeds instead of getting anything done, running the whole gamut from 800Hz to 4.7GHz. 

 

I was fairly confident in my cooler installation but just in case I redid it and nothing's changed. Right now I manually clocked the problem core down in Intel Extreme Tuning to where it doesn't cause thermal throttling anymore. It's now boosting to about 4.4GHz instead of 4.7 and the temperature spikes are still happening, but now only reach 96 degrees or so... >.> 

 

System info:
mobo: Asus Prime z390-a

cpu: i7-8700K

ram: 32GB HyperX Fury at 3733MHz (2x16GB)
gpu: EVGA 1080 Classified

psu: Cooler Master 850

cooler: SilentiumPC Fortis 3 v2 (cheap-but-pretty-good, if you don't know the brand. I am planning to upgrade to either Noctua NH-D15 or an AIO)
case: SilentiumPC Regnum RGB (full mesh front, glass side panel; Currently both the front and side are off)
case fans: 3x intake, 3x exhaust 

 

The only OC on the system is the XMP and the one core being clocked *down*

[Heliian]

I think your cpu is dying but try updating the bios and mobo drivers. 

[Impatient Traveler]

Freshly updated on both fronts, there's nothing newer.

[tdkid]

i would say that the liquid metal you used has dried out and needs to be replaced but there has not been enough testing on liquid metal to say that you should replace it every X amount of time. i would also download CPU-Z as it seems to be more reliable and accurate to what you are trying to look for. depending on how often you replace the thermal paste between the CPU and cooler, that might be your problem in that the thermal paste didnt spread correctly but i have to agree with helilan in that your CPU is dying. the CPU was released in 2017, you bought it used in 2019 is my guess so what happened between those 2 years and why was the original owner selling it. you should not be having an issue because i have an i7 8700k on an MSI z370 gaming plus board.

[Impatient Traveler]

Thanks for the input! 

I was considering getting the liquid metal replaced, I have no idea how the longevity is on that but it seemed like the logical choice. 

Thermal paste between the CPU and cooler isn't the issue - It was freshly installed last week, and then redone over the weekend. Taking the cooler off let me confirm it was maknig good contact, and the paste is nice fresh Kryonaut. 

As for why the previous owner was selling it, it was an upgrade on his end. The vibe I got was that it was an enthusiast with money to spare and he was going 9th gen or something.

One thing I've found when googling for this was people saying that temperature readings shouldn't be able to go up and back down as quickly as they are in my case and therefore that it was likely a faulty temp sensor. Anybody got input on that possibility?

Also I do have CPU-Z but afaik that shows clocks but not temps.

 

EDIT: I checked and the CPU was bought new on the 19th of November 2018. Obviously I never had a warranty due to the modification that had been done to it, but I do have a proof of purchase.

Edited June 21, 2021 by Impatient Traveler

[tdkid]

if he was going from 8th gen to 9th gen then he was an enthusiast with money to spare or an idiot because that is not that much if any of an upgrade. going from 2nd gen to 8th gen like i did is an upgrade but going from last years to this years is not. kind of like how people switch their iphones every year or every other year. just a stupid move and waste of money. 

 

it might be a faulty sensor i can not say for sure but it seems like the most logical option when the temps are jumping up and down 60 degrees. 

[CryingWimp]

IMO replace the old liquid metal with a decent thermal paste, use whatever you used for your cooler. Liquid metal is nice, but you'll never notice the difference if your not trying to reach maximum OC for benchmarks.

 

If you don't have a seal for the IHS, the CPU socket retainer will hold the IHS to the CPU. Just remember when you remove it later that the IHS can fall off  Only do this if your thermal paste is none conductive though. (Kryonaut will be perfect)

 

Do an extra good job cleaning the liquid metal, I'm not sure about the design of a 8700k but many CPUs have components exposed beside the die that would fry if shorted.

 

With bad liquid metal or thermal paste, massive temperature swings are very much possible, with no thermal paste a CPU can go from ambient to throttling in a second. There could be 0 contact between part of the die and the IHS if the liquid metal has gone real bad.

[Impatient Traveler]

Thanks! I was thinking about having the liquid metal replaced by someone that does it on the regular - I don't wanna mess it up, plus it'll cost about as much as a jig that I'd probably never use again. Though I am a little scared to just hand it over to someone I don't know, plus I can't exactly dismantle the computer for a long time as it's my only one *and* my work machine...