The tstat is 3 years old (i ordered it from a reccommended website on here that I cannot recall). I did remove it and inspect when flush/fill, but did not check to ensure it will open. I am pretty confident it will open, I just have not had success of getting the temperature hot enough. I let the car idle for about 25 minutes following the flush, but could only get it up to 160, outside temperature was about 45. I will try the cardboard trick willwren recommends.
Could I get it to circulate by idling without the tstat in, or could that cause problems?