I was troubleshooting a stuttering problem and decided to replace the CPU's thermal paste to rule out overheating. Before doing that, idle temperatures were around 40°C, but now they sit at 65–70°C and reach 100°C during games. I'm using an AIO liquid cooler. Its fan is spinning, and one tube feels warmer than the other, so I assumed the pump was working, although I'm not sure how to verify that properly. I've already reseated the cooler and reapplied the paste, but the temperatures are still high. Could this be a pump problem, a blockage or air pocket, poor mounting pressure, or an issue with the CPU_PUMP connection?
4 Answers
An air pocket is another possibility, especially if the radiator or pump position allows air to collect in the block. With the system powered off and handled safely, inspect the radiator orientation and listen for unusual bubbling or rattling from the pump. Don’t continue stressing the CPU at 100°C while diagnosing it; use a known-good cooler if possible.
Verify that the pump cable was not accidentally unplugged or moved to the wrong header while working inside the case. The BIOS should usually show an RPM reading for the pump. If it reports zero or an unusually low speed, reconnect it and check the header settings. If the connection and mounting are correct but the CPU still reaches 100°C, the AIO may have failed or developed a blockage.
Since the problem started immediately after removing the cooler, check the mounting pressure and contact first. Remove the block, clean both surfaces, apply a small amount of suitable paste, and reinstall it by tightening the screws gradually in a cross or star pattern. Even a small gap between the cold plate and CPU can cause temperatures to jump dramatically.
The AIO probably isn’t circulating coolant correctly. A significant temperature difference between the tubes can indicate a failed pump, blockage, or trapped air. Check the BIOS or motherboard monitoring software to confirm that the pump is connected to the CPU_PUMP or appropriate fan header and that it reports an RPM. Also make sure the pump is running at the expected speed.
If the pump RPM looks normal, the next things to check are air trapped in the block and whether the cooler is mounted firmly and evenly. A replacement air cooler can be a simpler and more durable alternative if the AIO has failed.