Radiators provide heat by circulating steam or hot water, and they're a feature of many home heating systems. If the radiator isn't heating properly, some parts of the house will be cold, and heating energy is wasted.
If your radiator isn't getting hot, the problem might be a clogged air vent. This is a common issue for steam radiators with a one-pipe system, which are supposed to bleed air as steam fills the system and shut automatically when steam reaches the vent. You might be able to clear a clogged air vent by boiling it in a water and vinegar solution, but in most cases you'll need to replace the air vent, says the Department of Energy.
Clogs in the pipework can also prevent a radiator from heating up. Over time, the water inside the pipes and the radiators corrodes the metal, leaving sludge deposits inside the system. To fix the problem, you'll need to chemically clean or flush the system to remove the deposits, says Fox and Co. Radiator Repairs.
Locate the pump near or inside the boiler. If the pump is operating normally, it should be whirring and vibrating as the motor forces water through the pipes. If the pump isn't working, it might be jammed. You might be able to fix the jam simply by tapping it lightly with a hammer or wrench. Alternatively, you can turn off the power, remove the pump's cover and remove the large screw in the center. There should be a second screw beneath it that you can turn to fix the jam, says Fox and Co. Radiator Repairs.