If your radiator is not putting out the heat you would expect, or if there is a difference between the heat at the top and bottom of your radiator, bleeding it will solve the problem. When your heating system sends hot water through the pipes and into your radiator to heat your home, air can get into the system, rise to the top of the radiator and become trapped. Getting the air out of the system will allow full hot water flow, and restore the radiator to prime working condition. It's a simple process you can perform in just a few minutes.
Turn off the thermostat for your house to shut off the system. Wait for the radiator to cool sufficiently so you can touch it.
Open the valve at the top of the radiator, using a radiator key or screwdriver, depending on the type of valve. Use a rag to protect your hand. Open the valve by turning it counterclockwise. Turn slowly to allow air to escape. Keep the pan under the valve.
Turn the valve clockwise to shut the valve once the air has escaped and water starts to come out of the valve. Be careful as the water could be hot. The air rises to the top and comes out first; once the water comes out the radiator has been effectively bled.
Turn the thermostat back on.