8700K + H100i V2 High Temps

Oct 9, 2018
First, here's my PCPP link: https://pcpartpicker.com/list/WMM72R

CPU is not overclocked.

So the PC was built around last July, with the mobo + CPU upgrade in December. Upon installation in December, the PC ran great. CPU temps were ~30-35C idle with a gaming temp of ~60-65C and a Prime95 stress test of around 85-90C. Then about two months ago (roughly mid August beginning of September) I noticed while playing Destiny 2 the temp was around 70-80C and fluctuated sporadically throughout playing the game. Also realized at this time that the idle temp was around 40-50C and Prime95 was 99C+. Ambient temperature during this entire time was around 20-23C and the PC is in an open area. My fan configuration is x3 120mm on the front pushing air into the AIO, and x2 140mm at the top and x1 120mm at the back bringing air out of the case. Ambient MB temp is normal. Decided to take the first diagnosis route and reapply thermal paste, using Arctic Silver 5. Reapplied, re-seated the AIO cooler, and the temps were completely back to normal! Idle was back to 30-35C, Destiny 2 was running at 60C and Prime95 was back to 85-90C.

Then two weeks have passed, and the temperatures are almost running as hot as before the thermal paste reapplication.

I currently have two working theories:

a.) AIO cooler pump is starting to go, however, the tubes seem to be fine (one warm, one cool) and the temperature in the Link 4 software does not indicate that the temp is hotter than usual or the pump is malfunctioning.

b.) Something is wrong with the CPU, however, all voltage levels seem fine and game performance is not affected during any of this.

Is there anything else it could possibly be? I just don't understand how after TP reapplication, the temps were fine for two weeks and then they were high again.

I appreciate any help, as this is starting to be frustrating.


Feb 11, 2015
I think that when you did the thermal paste over again it coincidentally fixed an air bubble problem because maybe the case was turned sideways, moved around, etc. Are the tubes on the bottom when the radiator is mounted? What about the tubes at the cooler? I think that is the best position to avoid air bubbles.
Sep 29, 2018
Can I please say to not base your temperatures on Prime95. Prime95 produces unrealistically high loads on your CPU and can potentially damage it. There is no real program that will put the stress on your CPU that Prime95 does, hence the insanely high temps. If you are playing Destiny at around 60C, then your cooler is performing perfectly as advertised, no need to worry about Prime95 temps...



On behalf of Tom's Moderator Team, welcome aboard!

As mortemas suggested, when you reapplied thermal compound you may have moved a bubble. However, it's more likely that you loosened some sediment causing a blockage to migrate. Unfortunately, you can count on it to occur again. All AIO's will fail ... it's not a question of IF; it's a question of when.

AIO's frequently fail due to:

(1) Inferior pump quality.
(2) Galvanic corrosion due to dissimilar metals, creating sediment in the coolant that creates blockages.
(3) Manufacturer's failure to adequately flush the radiator prior to final assembly.
(4) Manufacturer's failure to assure adequate coolant level.
(5) Low coolant level due to "permeation" where coolant slowly evaporates through the tubes over time.
(6) Accumulation of algae growth.

Unlike custom loops which typically use high-end pumps, copper radiators with copper water blocks, and allow for cleaning and coolant replenishment, AIO's use low-end pumps, dissimilar metals, (aluminum radiators with copper water blocks), and aren't designed to be cleaned or replenished. Dissimilar metals cause galvanic corrosion which creates sediments that develop over time. The accumulation of sedimentary particles of varying sizes in the radiator and pump can migrate throughout the loop when the computer is moved or re-positioned, or simply when flow is reestablished as the computer is once again powered up.

Other contaminates such as algae can combine with particles that are readily caught in the water block's micro-grooves, which decrease water flow through the grooves, thus reducing the water block's thermal efficiency and increasing processor temperatures. The accumulation of larger contaminants can jam the pump's impeller which is often the cause of many AIO failures.

Corsair has a decent 5 year warranty, so you might want to consider requesting an RMA replacement.

Once again, welcome aboard!

CT :sol:


Apparently, no one sent you the memo. You're not alone, so don't feel singled out. Respectfully, you don't appear to be well informed, so let's expand your perspective. The issue with Prime95 is strictly version dependent relative to processors with AVX Instruction sets.

For the record, and for the benefit of others who are unaware, there is nothing wrong with Prime95 VERSION 26.6.

When discussing Prime95, a blanket or general statement only serves to confuse the community. While your statement is true concerning later versions, Prime 95 v26.6 is actually the most ideal utility for thermal testing. Here's why:

“Stress” tests vary widely and can be characterized into two categories; stability tests which are fluctuating workloads, and thermal tests which are steady workloads. Intel tests their processors at a steady 100% TDP workload to validate Thermal Specifications.

Prime95 version 26.6 Small FFT's is ideal for CPU thermal testing, because it's a steady 100% workload with steady Core temperatures that typically runs Core i variants with Hyperthreading and Core 2 processors within +/- a few % of TDP. No other utility so closely replicates Intel's test conditions.

Utilities that don't overload or underload your processor will give you a valid thermal baseline. Here’s a comparison of utilities grouped as thermal and stability tests according to % of TDP, averaged across six processor Generations at stock settings rounded to the nearest 5%:

Higher TDP tests produce higher Core temperatures. All tests will show 100% CPU Utilization in Windows Task Manager, which indicates processor resource activity, not % TDP workload. Although actual Power dissipation (Watts) varies with Core Speed, Core voltage and workload, Prime95 v26.6 Small FFT’s always provides a true and steady 100% workload, whether you’re running stock or overclocked.

2nd and 3rd Generation i7, i5 and i3 CPU’s have AVX (Advanced Vector Extension) Instruction Sets, while 4th through 8th Generation i9, i7, i5 and i3 CPU’s have AVX2 Instruction Sets. Prime95 versions later than 26.6 run AVX codes on the CPU's Floating Point Unit (FPU). 2nd and 3rd Generation CPU’s are minimally affected by AVX, but 4th through 8th Generation with AVX2 may experience unrealistic temperatures up to 20°C higher.

Many 6th, 7th and 8th Generation motherboards address the AVX problem by providing offset adjustments (downclock) in BIOS. -3 (300 MHz) or more may be needed to limit Core temperatures to 85°C. Since 4th and 5th Generation don’t have AVX offsets, you can create a BIOS Profile for gaming, and a downclock Profile for AVX apps such as rendering or transcoding. If you’re overclocked, you may also need to upgrade your CPU cooler and case fans.

AVX codes can be disabled in Prime95 versions later than 26.6 by inserting "CpuSupportsAVX=0" into the "local.txt" file in Prime95's folder. However, since Core temperatures will be the same as 26.6, it's easier to just use 26.6. AVX codes don't affect Core i 1st Generation, Core 2, Pentium or Celeron processors since they don't have AVX/2 Instruction Sets.

As you can see from the table above, Prime95 versions later than 26.6 impose an absolutely brutal workload, which is extreme overkill for thermal testing at nearly 130% TDP workload. For AVX stability testing, RealBench is an excellent utility.

It's all explained in here: Intel Temperature Guide - http://www.tomshardware.com/forum/id-1800828/intel-temperature-guide.html

Give it a read, and in the future when discussing Prime95, offering a more thorough explanation will go a long way to help everyone get a better understanding of the topic of thermal testing.

CT :sol:


I'd like to make our readers aware that as per your statement, and as shown in the table above, Intel Extreme Tuning Utility (IETU) is only about 80% TDP workload, which is why it compares reasonably well to the heaviest CPU intensive gaming workloads. Here's another way to look at IETU:

Shown above from left to right: Prime95 v26.6 Small FFT's, Intel Extreme Tuning Utility CPU Test, and AIDA64 CPU Test.

Intel Extreme Tuning Utility is a fluctuating workload that peaks at about 80% TDP. Note the steady thermal signature of Prime95 v26.6 Small FFT's, which allows accurate measurements of Core temperatures. A steady 100% workload is key for thermal testing so the CPU, cooler, socket, motherboard and voltage regulators can thermally stabilize.

AIDA64 has 15 possible stress test selections which yield 15 different Core temperatures. Although the individual CPU test is a steady workload, it's just 70% TDP, which is unsuitable for thermal testing. Only the CPU+FPU test combination is about 100% TDP workload. All other AIDA64 test selections are fluctuating workloads, which like gaming, are less than ideally suited for thermal testing.

With respect to those who run apps such as rendering or transcoding, these real-world AVX workloads typically exceed worst case gaming workloads, and can approach levels on par with that of RealBench (AVX), AIDA64 CPU+FPU, and P95 v26.6.

Bottom line? If you can run P95 v26.6 Small FFT's under 85°C, then you should be able to run any app under 85°C. Gaming will of course run considerably cooler, and can vary greatly among different titles according to how CPU / GPU workloads are allocated.

CT :sol: