Right, that's the biggest factor--the fans exhausting hair from the radiator is nice and cool. When I was replacing the thermal paste, I shook the case a bit to see if I can hear the coolant move/slush around in the radiator, as I recall that I could hear it fine in the past when I moved my rig outside to blow off dust from fans. I'm leaning towards the radiator running low on coolant or something causing it to not circulate the coolant. The room temperature is about 60-66F, sometimes cooler, so environmental factor can be checked off.
I've been looking into getting a replacement, so hope that one will do better. Do you have any thoughts on the DeepCool Castle 240EX?
Thanks!