...at least twice a year you should drain the radiators - If "Hot Water Return", drain the return tank above the boiler, then open the air valve on top corner of each radiator and let air seep out into a cup until a stream of hot water comes out...be sure to close after (start with the furthest radiator for the boiler and work your way inwards to the middle of the house).
- If "Steam", go down to the boiler and look at the glass cylindrical tube on the front or side of the boiler: open the drain valve and let the water flow out into the floor sewer until the water level is at mid-level of the tube. WHAT YOU HAVE PROBABLY SOUNDS LIKE WORLD WAR III in THE MIDDLE OF THE NIGHT! I have had all of the above problems and usually the fixes I suggested work!