Two months ago we moved to a two story home built in 1968. It has gas/hot water baseboard heat (two zones) with a Burnham boiler. In each room the baseboard runs the entire length of a wall, as much as 20 feet in the living room. When the heat kicked on for the first time, it made various loud noises and you could hear water rushing through the system. The first professional said the system was airlocked and water logged. He bled the system and drained the tank. This didn’t solve the problem. The second professional said the pressure valve was broken. He replace the valve and this eliminated the sound of water rushing through the system. However, the system still makes noise loud enough to wake us up at night (pings, bangs and sometimes crashes). Someone suggested installing an automatic bleeder. Someone else suggested the size of the baseboards could be the problem. Any suggestions?
Once the water pressure inside the system has dropped low enough to admit air, it often takes time before the entrapped air is removed. If the system does not have a diaphragm expansion tank and an automatic air vent, or a properly installed non-diaphragm tank and air elimination system, several purges of air may be required.
Call the repairman to eliminate the remaining air that is causing the banging.