Broken water radiator pipe fixed, but produces no heat!

If this is not the best forum for this querry, please redirect me.

I live in a three story row house built around 1960 with a water based radiator heat system. In January water started leaking into the bottom floor apartment. It turned out that a pipe imbedded in the wall and feeding water to the radiator below was cracked (frozen?). A plumber came in and broke the wall above the radiator and welded a new pipe in place, but now there is no heat from that radiator even though the radiator in the next room provides heat; as my plumber is currently unavailable, does anyone have any ideas as to what the problem might be, before I plunk down more money for another plumber?

Thanks.

Your radiator is air bound.

Yes, it's air locked. Do you have a bleeder at the top? You should. Open that bleeder to let the air escape.