Radiators in the home work on a steam system. Steam is produced from a boiler and sent through pipes to the radiator units. The radiators heat up and let off a radiation of heat. If there are air bubbles or excessive water condensation in the system the steam will not reach the radiator unit and will cause heating issues. Excessive pressure in the system will cause rattling and the potential for bursting pipes. Maintain your radiators regularly.
Bleed your radiator by inserting or connecting the bleeding key to your radiator's air vent valve. Some radiators have a turn valve that does not require a bleeding key. Turn down the thermostat and place a rag underneath the radiator. Open the vent using the key. Close the vent once air stops coming out of the radiator. Turn the heat back up.
Inspect the unit for leaks using a mirror to look behind the radiator and around tight corners. Drain the radiator and remove paint and rust from the area of the leak using sandpaper. Make a rough surface for the patching compound using a file. Use a metal patching compound, such as JB Weld, mixed to the product specifications and apply to the radiator at a thickness of 1/32 inch. Allow it to dry for 24 hours before turning the radiator back on.
Replace a leaking or clogged air vent by first turning off the radiator. Unscrew the old air vent from the radiator by hand turning it counter-clockwise, wrapping your hand in a towel if it is hot. Wrap a bit of Teflon tape around the threads of the new air vent and place it on the radiator.