I have a Ryzen 7 5800X with a Noctua NH-U12S redux cooler. Even relatively light games such as Minecraft and The Binding of Isaac make the CPU climb to around 90°C, where it stays. This has always happened, and cleaning the PC and replacing the thermal paste did not change anything. The cooler fan is spinning and appears to be mounted evenly.
The system is built in a Kolink Observatory Lite case with three front intake fans and one rear exhaust fan, but the front panel is glass. Removing the front panel did not make much difference. Could the cooler be mounted incorrectly or simply be insufficient? Is the case airflow the main problem, and what kind of replacement case would be better?
4 Answers
A dual-tower cooler would give you more thermal headroom, especially if the processor is running PBO or sustaining high power. However, a good airflow case and correct settings should come first. Seeing 90°C does not automatically mean the CPU is damaged—the 5800X can boost until it reaches its thermal target—but it is worth checking whether it is actually throttling and whether temperatures are unusually high for your CPU's power draw.
That case is a likely contributor. Front fans behind a solid glass panel cannot bring in much cool air, so the cooler is trying to use already-warm case air. For a replacement, choose a case with a genuinely open mesh front, sensible fan mounts, and at least one rear exhaust position. A second fan on the NH-U12S can also help, but improving the restricted front intake is more important than adding fans behind the glass.
Run a quick comparison with the side panel off while monitoring temperatures. If the result improves substantially, the airflow is the problem. If it still immediately reaches 90°C, revisit the mounting pressure: remove the cooler, clean both surfaces, apply a small amount of fresh paste, and tighten the two screws alternately so the pressure stays even. Also verify that the fan is connected to the CPU_FAN header and that its curve actually increases with temperature.
The NH-U12S redux should generally handle a stock 5800X, although Ryzen 5000 chips are designed to boost aggressively toward their temperature limit. Since you already replaced the paste and the mount looks good, test the PC with the side panel completely removed. If temperatures are still reaching 90°C, the case probably is not the only issue. Also check CPU package power, clocks, and whether PBO or a manual overclock is enabled. PBO can be active through BIOS defaults on some boards, and setting a power limit or using Curve Optimizer with a negative value can reduce heat.
I already removed the front panel and saw almost no change, but I will test it with the side panel off too. The cooler has two screws, and I tighten them alternately so it stays level.