- 1). Turn the thermostat off. Turn off the valve at the base of the radiator.
- 2). Wrap a towel around the steam vent. Gently unscrew the steam vent from the end of the radiator by turning it counterclockwise as you face the radiator. Be careful not to break off the steam vent.
- 3). Examine the steam vent. If the opening has a clog or if the brass bellows inside aren't able to move freely, this vent is probably hissing or whistling. There may not even be steam for heat moving into the radiator.
- 4). Wrap Teflon tape around the threads of the replacement steam vent. Insert the threads into the opening on the radiator and turn the new vent clockwise. The vent holes must be facing up in order for the new vent to work properly.
- 5). Remove the valve handle by pressing down on the screw and unscrewing it while you pull up the handle. A leak here also causes the radiator to hiss and to lose heat.
- 6). Locate the valve nut under on the threaded piece below the valve handle. Use a crescent wrench to turn the valve nut counterclockwise to remove it. Wrap graphite packing around the threads where you just removed the valve nut. This creates a new gasket to seal the valve nut in place.
- 7). Reattach the valve nut securing it with the crescent wrench. Replace the valve handle.
Source...