Question Air-cooled CPU temps suddenly high after 3 years, out of ideas

[vElectrixx]

The cooling on my setup has always been great. I've had all 12 cores at 4.3GHz and never had it exceed ~75C at full load. Idle was probably low 30s.
At some point, temperatures suddenly skyrocketed. At base clock, it idles at 55C. Full load floats between 88-93C.

Things I've tried:
-Dusting, although I do this every two weeks.
-Checked fans. Both CPU fans are working flawlessly.
-Reapplied thermal paste.
-Bought brand new thermal paste and tried applying that.
-Complete reassembly, thinking maybe the heatsink's mounting failed and became a bit loose.
-Leaving the side panel open and having a large metal room fan blow into it had zero impact on the temperature.

One strange thing I noticed was the lack of noticeable heat transfer occurring. At full load ~90C, I touched the pipes at the base of heatsink. They were not hot. The heatsink itself is not broken at all though, so there's no way it's the source of the problem.
I'm a bit worried it's actually a temperature sensor problem, but is it really that common of an issue?

Spoiler: Specs

CPU: AMD Ryzen 3900X
Cooler: Noctua NH-D15 w/ Thermal Grizzly Kryonaut
GPU: EVGA FTW3 ULTRA GAMING GeForce RTX 2080S
MB: Asus ROG Crosshair VIII Hero (WI-FI)
RAM: Corsair Vengeance LPX DDR4 64 GB (4 x 16GB)
PSU: EVGA SuperNOVA 850 P2

A bit unrelated, but I nearly destroyed my CPU while removing the heatsink. It was so stuck that, despite my efforts to gradually twist and pull off the heatsink, the CPU was ripped out of the socket and thrown across the room upon removal. Several pins along the edge had bent but were easily fixed, thankfully.

 

[Lutfij]

Can you check and see what BIOS version you're on for your motherboard at this moment of time? I'd also open up Task Manager and see what your system resource usages are like when idling.

A bit unrelated, but I nearly destroyed my CPU while removing the heatsink. It was so stuck that, despite my efforts to gradually twist and pull off the heatsink, the CPU was ripped out of the socket and thrown across the room upon removal. Several pins along the edge had bent but were easily fixed, thankfully.
AMD CPU's need to be heated up, powered up, and then shut off to cause the thermal paste to be fluid, then you use a twisting motion to take the cooler/block off the processor - not in an upward motion though.

 

[vElectrixx]

Can you check and see what BIOS version you're on for your motherboard at this moment of time? I'd also open up Task Manager and see what your system resource usages are like when idling.

Should've included that in my list. I've also double checked all drivers and updated everything, including the BIOS.
So BIOS: v4501

CPU idled at ~1% with minimal extra processes running. Sat around 52C.
Reopening Firefox briefly spiked the CPU to 8% & 68C

AMD CPU's need to be heated up, powered up, and then shut off to cause the thermal paste to be fluid, then you use a twisting motion to take the cooler/block off the processor - not in an upward motion though.

Lesson learned. It's my first AMD CPU in ages.

 

[BFG-9000]

At full load ~90C, I touched the pipes at the base of heatsink. They were not hot. The heatsink itself is not broken at all though, so there's no way it's the source of the problem.

Heatpipes don't last forever. Given how they are made, the solder sealing the ends can eventually crack from thermal cycling to both let in atmospheric pressure and let out the water vapor, which turns it into a plain copper pipe. Fortunately Noctua offer a 6-year warranty on the NH-D15 so if it's a manufacturing defect you are covered. The best way to prove that is to use a thermometer to show that one of the heatpipes isn't working, as usually only one of them will break.

While 93C isn't unusual for a modern processor that can overclock as many cores as it has thermal headroom for, the NH-D15 is quite large and it's really rare to see a 3900X on one go over 85C--the 75C you had originally is what they usually run at so something is seriously wrong.

 

[beyondlogic]

Heatpipes don't last forever. Given how they are made, the solder sealing the ends can eventually crack from thermal cycling to both let in atmospheric pressure and let out the water vapor, which turns it into a plain copper pipe. Fortunately Noctua offer a 6-year warranty on the NH-D15 so if it's a manufacturing defect you are covered. The best way to prove that is to use a thermometer to show that one of the heatpipes isn't working, as usually only one of them will break.

While 93C isn't unusual for a modern processor that can overclock as many cores as it has thermal headroom for, the NH-D15 is quite large and it's really rare to see a 3900X on one go over 85C--the 75C you had originally is what they usually run at so something is seriously wrong.

agree with this heatpipes can fail eventually takes a while but the liquid in the pipe can eventually fail. cracking of pipe etc.

you said the cpu was also ripped out the socket with cooler thats a bit of a worry it could also mean that the heat spreader or ihs may have come a bit loose from the cpu itself and not making contact with the heat spreader which means it cant dissipate heat to cooler.

cant really confirm until you try a diffrent cooler though.