Did you ensure the air was bled out of the cooling system? Running it with the cap off doesent always bleed it out. There are two bleeder screws, i usually just need the one on that black rail that runs in front of the header. Leave it running and have the screw open until just coolant comes out, if no coolant comes out for awhile its a good sign there was lots of air in the system. Make sure those 2 hoses coming from the rear of the engine to the firewall are not switched up. Also while its running squeeze the thick coolant hoses, [upper/lower/and thermy] hoses and it might gurgle and get it moving, worked for me, check if the hoses are getting hot at all after running it for a few mins..