Hello,

You can try setting the pump to full/less fast using the NZXT software.

The pump should also be below the radiator (the highest point of the radiator should be above the CPU part). This is so that the air bubbles in the pump (of the CPU block) can be evacuated on the way up and remain stuck in the radiator.
You can also try to tilt the case sideways to let the bubbles out.

Hi,

NZXT and most other brands have been showing the wrong way of mounting radiators for years.
Watch this video to see how it works and the correct way to do it no matter where you mount your radiator.

https://www.youtube.com/watch