Overheating issue

[bigmiketx]

I changed out the radiator on 2005 dodge caravan i went from open system meaning one with radiator cap to closed one where you add in in reservoir no radiator cap when i started it up it sent needle up to hi temp quick.I was wondering could the be air in system or something cause i put the old radiator back in it did the same thing and if so how would i go about getting it out and refilling it properly?