I noticed with mine that if I pushed down on one of the lines and let it go, as it sprung back up there was the same sound. After doing it a few times it starting to sound quieter and stopped so me thinks there might be some air in the system and doing what I did pushed it (total guess here) into an engineered area for air to collect...like a partially empty resevoir. Again, total guess on that though...but temps don't exceed 47c under load at 3.68ghz