steam heat

I had my old steam heat boiler replaced last fall with a higher effeciency boiler model number PIN4SNI-HE2. The boiler was also moved a few feet. Since then, when I turn the heat on and the boiler fires and all is still cold, boiler near pipes, pipes, radiators, I hear a noise for about ten minutes coming from all the radiators. I can only describe it as a stealy noise of water flow. This noise is not addressed in Dan's book "We Got Steam Heat" nor can my contractor or boiler manufactur determine its cause. Has any one come across this noise before?