It is time to troubleshoot steam heat radiator problems when you discover a puddle near the radiator, when it's not producing heat, or when it's making a pounding sound each time it fires up. In steam heating systems, the furnace heats water in a boiler until steam is formed. This steam flows through pipes into radiators which are located throughout the house. When the steam in the radiators condenses into water, it returns to the boiler to be heated. There are basic maintenance issues that can cause radiators to leak water, lose their heat or operate noisily.
No Heat from a Single Radiator
It is possible that air is trapped in the radiator, so when the radiator is cool, open the bleed valve at the top of the radiator; close it again when water begins leaking or squirting from the valve. There could also be a faulty or clogged inlet valve at the radiator foot. The water pipe leading from the floor to this valve and then to the radiator should be hot to the touch. If the pipe running from the valve to the radiator is cold, the valve itself could be clogged or stuck in the closed position. Clogged valves should be replaced.
No Heat from Boiler
Check the fuse box or service panel, and if needed, reset the breaker or replace the fuse. You can then check the pilot light, which may be out, or the electronic ignition if there is no pilot. Then, make sure the boilers water level is correct by checking the water pressure, which should be between 12 and 15 pounds per square inch (psi). If the pressure is too low, open the fill valve until the pressure reaches 12 psi. Finally, check to make sure the thermostat is set to "heat" and reset the temperature.
Water on Floor Neat Radiator
If you discover water on the floor near the radiator, then the cap nuts that are used to fasten the inlet valve may have come loose or be corroded. Turn the system off, then tighten the valve nuts; if this doesn't work, replace them.
A knocking sound is often due to the improper pitch of the pipes. All pipes must have a downward slope so that the water may flow without difficulty from the radiator to the boiler. If, for some reason, a piece of pipe has sagged, water will collect in this depression and become a serious obstacle in the path of the oncoming steam. The meeting of the steam and the trapped water results in pounding. When it occurs near a radiator, it can generally be eliminated by putting small blocks of wood under the legs of the radiator. This will increase the pitch of the radiator and the pipe connected with it so that the water will find an easy path back to the boiler. When hammering occurs in some other part of the system, try to find the section of pipe that has sagged, causing a hollow where water can collect.
If you are still unsure as to what the cause of your problem is, it is best to contact a qualified technician to examine the entire system.