I tried leaving my setup over night for leak testing before I first installed it and the water temp was about 5 degrees C above ambient in the morning, but the Eheim 1048 ain't a 500 gph pump.. 600 l/h corresponds to 120-130 gph ? (I feel sorry for those not using the metric system

)
With the fan on and the system installed in the case, I only had at most one degree above ambient. It's time to replace my puny rad soon and this issue will be even more moot.
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Pump:Eheim 1048,
Radiator:LPD radiator 100x150x20mm,
CPU block:DD Maze-2,
GPU block: DD GPU block,
Chipset block:Zalman NB32
AMD XP 1500+, EpoX 8K7A, PoV GF3Ti200
Pic of my YY-cube