#1 Double check the belts
#2 Make SURE all of the air is out of the system!
#3 Make sure you put the thermostat in facing the correct way
#3 If the above do not fix it - and i really doubt this - try this - By pass the heater core with a short peice of hose (basically a "U") So where the coolant comes from the engine and goes into the firewall and heater core and comes back out of the heater core to return to the engine - we want to bypass the core all together.
Still i have a tough time imagining the issue is here - but the lack of heat is another indicator.
2005 Rubicon Unlimited Sahara #609 of 1000. 4 speed auto. Sirius Sat Radio, Mile Marker PE8000 Winch, 2" BB from Rocky Road, 32" BF Goodrich Radial TA/KO, RB1 NAV Radio with Ipod Controller