Can you feel hot air being pumped by the fan when the car is running ? Which fan? Heater fan inside - yes. Main radiator fan - yes, but it doesn't appear to increase when hot (that's why I replaced the fan clutch to begin with, plus it spun a few turns, didn't come to an "abrupt" stop, when the engine is turned off hot) Aux radiator fan runs with A/C on. Temp still wanted to creep over 1/2 even with aux fan on.

Are you sure that new clutch is good? Some people have reported getting a bad one. I could tell the difference right away when I changed mine, the sound was much louder as that fan started to really push the air around, kinda like a big truck, sorta like a "roaring" sound. Either that or there is something else not allowing that clutch to get hot enough to lock up. George Davis's suggestions sound good. I assume that it was bled properly with the heater on high while bleeding? T-stat is good and inserted properly? Hopefully others will have better advice for you, too.