Question - My Sears Coldspot frostless refrigerator and freezer whistles, wheezes and hisses. Sometimes it sounds almost alive - even humanlike. What do these strange sounds indicate? Is the refrigerator about to break down?
Answer - Your refrigerator's strange noises are probably coming from the evaporator fan motor located on the back wall of the freezer compartment. Usually before the evaporator's motor bearings give out, they will make chirping sounds. As the bearings continue to wear, the motor will produce strange noises similar to the ones you describe. Usually this means the fan motor is about due for replacement. A new fan motor kit can be purchased from any Sears parts store. Your local appliance center may also have a fan motor that would fit.
Question - Our home has an older gas-fired hot-water boiler, with a pressure regulator and a relief valve to maintain the proper water pressure. A 30-gallon cylindrical tank is slung horizontally from the ceiling over the boiler, and connected to the main hot-water line.
A small amount of water leaked from the relief valve drain on each heating cycle. The overhead tank was waterlogged and, assuming that it was intended for expansion of the heated water, I pumped air into it. This stopped the leaking from the relief valve, but resulted in several airbound radiators. Is this tank an expansion tank or an emergency source of water to the boiler?
Answer - The tank is an expansion tank and not an emergency water source. The water feed line to the boiler, with its pressure-reducing valve, will automatically feed water at the required pressure (12 to 15 psi) whenever makeup water is needed. In a hot-water heating system the distribution pipes, radiators and boiler are a closed circuit completely filled with water. When the water heats up it expands.
The additional volume of water flows into the expansion tank where it presses against a cushion of air - or in newer systems, against a diaphragm. Without an expansion tank in the system, expanding water would cause the pressure-relief valve to discharge.
When an expansion tank becomes waterlogged, the system acts as if there is no expansion tank, and the relief valve constantly discharges. To correct this, you have to drain the tank. In the process, an air cushion will be re-established. If you have an older style tank without a diaphragm, it should be drained completely. A diaphragm-style tank needs to be only about two-thirds drained. If there is a shutoff valve in the line between the tank and boiler, be sure to leave it in a fully open position after draining the tank.
Your airbound radiators are caused by pockets of air trapped in the system. To release this air, you have to bleed the system. All or some of your radiators should have small key-operated valves for this purpose. After the boiler has been operating for several hours, hold a cup under each valve and open it to release the air until you get a steady stream of hot water.
To submit a question, write to Popular Mechanics, Reader Service Bureau, 224 W. 57th St., New York, N.Y. 10019. The most interesting questions will be answered in a future column.