After repairing a pump seal, I let my cooling system run overnight. I was shocked to see the water temp this morning. It was 32.7 C with an ambient temp of 19.8 C. Since the computer was not on, no fans were able to provide airflow for the radiator. In addition, the 120mm fan that usually blows on the pump, as air enters from the lower front of the case, was not running. Normally with the computer running I see a maximum water temp of about 27 C. I am amazed at how much heat an inline pump can generate. It would be interesting to compare my results with other systems, specifically those with submerged pumps.