Most hot water radiators have a valve that opens with a special key. Beginning with the radiator at the end of the line, open the valve, holding a small vessel under the valve. Keep the valve open until the air escapes and you begin to get water coming out. Turn off the valve and go to the next radiator on the line. This is known as bleeding a radiator.
If you have a steam boiler, radiators have to be tilted just a tiny bit toward the end where the steam enters. Check with a level on the top of the radiator to see that your radiator isn't dead level. You can use a little wooden or plastic shim to raise the radiator about 1/4 inch on one end. There are several videos from This Old House on YouTube that you can view about how to do this.
Most hot water radiators have a valve that opens with a special key. Beginning with the radiator at the end of the line, open the valve, holding a small vessel under the valve. Keep the valve open until the air escapes and you begin to get water coming out. Turn off the valve and go to the next radiator on the line. This is known as bleeding a radiator.
If you have a steam boiler, radiators have to be tilted just a tiny bit toward the end where the steam enters. Check with a level on the top of the radiator to see that your radiator isn't dead level. You can use a little wooden or plastic shim to raise the radiator about 1/4 inch on one end. There are several videos from This Old House on YouTube that you can view about how to do this.