Quick Answer

High temps on a liquid-cooled CPU almost always trace back to poor mounting pressure, dried or improperly applied thermal paste, an undersized radiator for the CPU's TDP, or inadequate case airflow routing the radiator's exhaust back into the system. Each of these causes is fixable without replacing the cooler.

The Most Common Culprits: Mount and Paste 🔧

The single most frequent cause of unexpectedly high temps is an uneven or loose AIO cold plate mount. AIO cold plates must seat flat and evenly on the CPU IHS; a single overtightened screw corner can rock the plate, creating air gaps that raise temps by 10 to 20 degrees Celsius. Always use a diagonal tightening pattern and stop once finger-tight plus a quarter-turn. Thermal paste is the second culprit: AIOs ship with factory-applied paste that can dry, crack, or distribute unevenly during installation. On CPUs like the Ryzen 9 9900X or Core i9-14900K where the die sits slightly raised on the substrate, a thin, even pea-sized application of quality paste makes a measurable difference. Dried paste can add 15 degrees or more to peak temps.

Airflow and Radiator Placement Problems 💨

A 360mm AIO can only reject heat as fast as fresh air moves through the radiator. If your radiator is mounted as an exhaust but pulling in warm air from a GPU blower, or if the case has blocked intake vents, the coolant temperature rises and the entire system's thermal performance collapses. In South African summer conditions, ambient room temps of 30 degrees Celsius or above shrink thermal headroom significantly. Check that your case has at least two 120mm intake fans drawing cool air from the front or bottom, and that no cable bundles are obstructing airflow paths. Repositioning the radiator from rear exhaust to top exhaust often drops coolant temps by 3 to 7 degrees.

Radiator Size vs CPU TDP Mismatch ⚠️

Not every liquid cooler is rated for every CPU. A 240mm AIO on a 253W all-core Ryzen 9 9950X will genuinely struggle; the radiator surface area is insufficient to reject that heat load at acceptable fan speeds. If your cooler is correctly mounted and airflow is healthy but temps still hit 90-plus degrees under sustained load, the radiator size may simply be too small for your CPU's power draw. Stepping up to a 360mm unit from the R2,500 to R4,000 range is the correct fix in this scenario.

TIP

Re-Mount Before You Replace ⚡

Before spending money on a new cooler, remove and remount the existing AIO with fresh thermal paste. This single step resolves high temps in the majority of cases and costs only the price of a tube of quality thermal compound, around R150 to R300 at most.

FAQ

How do I know if my AIO pump is working correctly?

Open HWiNFO64 or your AIO's companion software and check pump RPM. A healthy AIO pump typically runs at 2,000 to 3,000 RPM. If the reading is zero or below 1,000 RPM, the pump header may be unplugged or the unit may be failing.

Can a high-TDP CPU damage an AIO if temps spike repeatedly?

Repeated thermal spikes above 95 degrees Celsius accelerate degradation of the pump bearings and tubing over time. It is best to resolve the root cause promptly rather than running with chronic high temps.

Does case size affect AIO cooling performance?

Yes. Smaller cases (mATX and ITX) have less internal volume and often more restricted airflow, which raises the ambient temperature inside the chassis. This raises the coolant temperature baseline, meaning the AIO works harder for the same result.

Still seeing high temps after troubleshooting? Check the full range of 360mm AIO coolers available at Evetech to find a unit properly rated for your CPU's thermal output.