I keep on hearing a rattling sound like metal banging from 1 section of pipe in my hydronic heating system, I tried bleeding but no improvement. Thanks
A lot of radiators on hot water heat systems, if not, should have what is called a coin vent. These are located at the high points of each radiator. If you do not have these, you need to have them installed. Otherwise you will not remove all the air in the lines and will always have noise in your piping and it will cut down on the efficiency of the unit.