Please help I've had this problem for a few years my down stairs radiators are grand , my upstairs ones when I'm bleeding them a little air comes out but no water ( no pressure) the header tank in attic is full and fills when u push ball cock down. Every time my heating turns on ( I have a riello boiler) it bubbles and bangs and sounds shocking this lasts up to a half an hour I really don't know what else to do and cant afford a plumber please help