What could be causing the poor temperatures with your Noctua NH-D15S?
What could be causing the poor temperatures with your Noctua NH-D15S?
I just purchased a Noctua NH-D15S from Amazon to replace my NZXT Kraken X61 because of concerns about pump failure, even though I thought it was a bad idea. I didn’t realize the temperature difference would be so significant. During a prime95 stress test, my CPU reached over 70 degrees Celsius and also hit 80, while idling stayed between 35 to 40 degrees Celsius. I have an Intel Core i7 7700k. Could this mean I installed the cooler incorrectly? Are these temperatures typical for this cooler with that CPU? I want to keep it in good condition. I’ve read that both this cooler and the NH-D15 can outperform AIO coolers. I’m really unsure what to do! Please help or at least provide a response.
Prime95 is built to push your CPU to its absolute limit. You could experience much higher temperatures with Prime95 compared to a normal real-world workload. Also, air doesn’t retain heat as effectively as liquid, so it will quickly reach its peak temperature and then drop back down to idle levels almost instantly, unlike liquid cooling which shows a gradual rise to maximum before settling. Consider this in the context of liquid cooling systems.
I think the CPU cooler might need to be reinstalled. The cooler could be losing good contact with the CPU, or the thermal paste might need to be reapplied.
The Noctua NH-D15 is considered one of the top air coolers. It's important to note that a CPU water cooler essentially relocates the heat sink, which can enable a bigger heat sink or even a larger radiator.
Another potential issue could be that the fan speeds are too low.
I've also been using the Noctua NH-D14 for a long time. I'm really satisfied with it.
Prime95 is built to push your CPU to its absolute limit. You may experience much higher temperatures compared to real-world usage when using synthetic loads. Additionally, air possesses a much lower specific heat capacity than liquid, which means it will quickly reach its peak temperature and then drop back down to idle levels almost instantly. In contrast, with liquid cooling, initial readings seem low before gradually rising to the full capacity over time—something you might notice if you're used to liquid systems.
Consider this from a liquid cooling perspective: understand these differences.
Also, ensure the thermal compound is evenly spread across the IHS (the processor die) for optimal contact. If it doesn’t fully cover the die—especially in the center where the cores are located—the temperatures may rise. Air bubbles in the paste, even tiny ones, can also contribute to this issue. This risk increases if you move the heatsink during installation, as it can affect contact quality. Aim for a balance: not too tight, but not loose either.
I experienced this with one of my fin heat-sinks; the metal base bent and caused uneven contact with the IHS, leading to slight wobbling. Once re-installed and re-applied, it settled more evenly.
It’s advisable to reapply thermal paste and consider using a method like the pea or dot technique, but avoid overdoing it—both excess and insufficient paste can hurt performance. If you’re using the original paste and have none left, Arctic MX-4 is suitable, while Thermal Grizzly “Kryonaut” (specifically) offers better reliability at a higher cost. The difference in temperature might only be a few degrees Celsius.
MX-4 has a thermal conductivity of 8.5 W/mK, whereas Kryonaut reaches 12.5 W/mK. Prices range from about $6 to $20 for roughly 4 grams.
After overclocking, Prime95’s peak temperatures should still be manageable, though they may feel higher than expected. At stock settings, temperatures should remain lower, but keep in mind Prime95 is known for exaggerating heat levels.
Reapplying paste and ensuring proper airflow from intake to exhaust fans will significantly improve results. Also, the room temperature plays a major role—if your environment is already around 35°C, an idle temperature of 35°C feels more reasonable.