ENGINE COOLING

Rotorua Morning Post, Volume 1, Issue 199, 15 April 1932, Page 2

ENGINE COOLING

SOME DANGERS PROPER TEMPERATURE MOST IMPORTANT FEATURE. THE COOLING SYSTEM. Probably the radiator and cooling system is the most neglected part of the car. Most motorists give it little or no attention, except occasional topping up with water or tigbtening of the pump-sbaft packing gland. Few seem to realise that the cooling system is not to prevent the motor from boiling or becoming objectionably hot, but to keep the engine at its best operating temperature, namely, about 185 degrees Fahrenheit. An air-cooled motor, whether aeroplane, motor-cycle, or car, has an exceedingly wide range of op'erating temperatures and consequently the d-e signers have tremendous difficulties to over-sufficient cooling under all conditions. A water-cooled engine does not operate nnder such greatly varying ranges of temperature, nevertheless the temperature may often exeeed that for which the cooling system was designed. The consequences of rnnning with a motor that is too cool are just as serious as if the motor were abnormally overheated. Overheating can be traced to many causes, such as faulty circulation of the water through the radiator and cylinder hlock and head of the motor itself. Other causes are slipping fan belt, too rich or too lean .a mixture, retarded spark, dragging hrakes, overfilled gearhox, or a motor that requires decarbonising. Another thing that is likely to produce overheating is the thermostat, for should this be out of adjustment it may prevent the free circulation of the water when the motor is hot. Radiator shutters, wh'ether controlled automatically or manually, which do not fully open will cause the motor to run hot. Usually there may be no visible evidence of overheating, but in serious cases the radiator will perhaps boil over or fum'es will be felt within the car.

Over-Cooling. Over-cooling is not readily noticeable, but is more serious than overheating. When the motor is running too cool the oil is sluggish and cannot be whirled into a fine enough spray to adequately lubrieate the cylinder walls. A cold motor requires a rich mixture (as evidenced when starting cold), but a rich mixture never completely hurns away, so raw petrol . is left on the cylinder walls, destroying the oil film and causing dilution. Radiator shutters that ara left wide open when the motor is cold allow the engine to remain cold. The shutters should be closed when the engine is cool, and gradually opened as the motoH warms up, and for this it is necessary to keep an eye on the engine temperature gauge. Similarly a damaged thermostat which allows the radiator shutters to open too soon, or allows the water to circulate too freely when the engine is cold, will not help the motor to reaeh its correct temperature. The majority of cars are run over-cool; it is only when they are driven fast on the open road that most of them are allowed to reach the correct temperature. Proper Temperature. Internal combustion engines give their greatest thermal efficiency when operating at a temperature of just over 185 degrees Fahrenheit. At this .temperature the greatest energy can be derived from the petrol, and the oil becomes fluid whilst still retaining the required viscosity and body. Below this temperature a richer mixture is required to develop the same power and flexibility, since much heat is dissipated by the cold metal of the engine. Overheating, that is, running at a higher temperature than about 185 degrees Fahrenheit, thins down the oil, with the result that there is more wear on the eylinders and bearings. Moreover, if the motor is too hot the gases entering the eylinders will be unduly rarefied. Overheating is exp'erienced in modern cars in good order only when they are put to hard pulling up steep hills, through sandy roads, or are driven at high speeds. How often does one bear from a motorist who has just completed a run of two or three hundred miles that his car ran sweeter than ever and pulled like a Trojan? The reason is that the engine was at a proper temperature, since on such a tour fast speeds are usually indulged in, together with heavy loadixig of the car with luggage. If a car runs best on a fast or hard run, it is a sign that under normal con ditjons it is over-cooled. Intelligent use ofthe radiator shutters will maintain correct temperature.