New Thermostat & Engine OH???

Since we bought this 96 EX, the overflow reservoir has been dirty and the coolant murky. Since I had some time after my O2 & Knock sensor bout, I drained the system, removed the old T stat, turned the heater control to highest heat setting, flushed water through the upper radiator port and out the lower hose. It was clean and clear the whole time as best as I could tell. Next I put in the new T stat with a new gasket, making sure the pressure release valve was up like the T stat I removed. I buttoned it all up. The problem I'm having is that the car can run 2min, 5min, 20 min and the thermostat isn't opening. The upper hos is getting hot and the lower (where the T stat is) is staying cold. I'm going to pull it out today and put a superstat in there. That way if this one sticks it will be open and not closed. Any other ideas on this situation?

Man, Civic folks aren't very helpful with problems. On the Isuzu forum I always get input. :sarcasmsign: Anyhow, after cross referencing how the hoses act on my Rodeo, I've decided that it seems normal for the upper hose to get hot (the non-t stat hose) and the lower to be cool (T stat hose). That isn't what the Haynes manual says, but oh well. On to the next issue. ;)