To give a large surface for radiation, fins are provided on the cylinders. Most motor car engines are cooled by water which circulates through jackets around the cylinders. After it takes up heat from the engine it passes to the radiator where it is cooled by air. In most cases the draught is aided by a fan. In the most common type of cooling system a pump provides forced circulation of the water. The pump is geared to the engine so that when the engine is running the water must circulate. In cold weather, the circulation of the water is at the same rate as in hot weather since it depends only on the speed of the engine. As a result, the engine on cold days will not reach a high enough tempera ture to operate efficiently. To overcome this condition, a thermostat between the engine and the radiator is usually used to control the amount of water which is circulated by the pump. In some instances thermostatically controlled shutters in front of the radiator are used to keep the engine coolant temperature from falling too low. Engine operation at temperatures below 140° F. decreases engine life through increased cylinder wear and contamination of the crankcase oil.
Freezing of the water in the cooling system may cause leaks in the radiator, and may crack the engine block. Methanol, formerly known as wood alcohol, denatured ethyl alcohol, glycerine and ethylene glycol may be mixed with the water in the radiator to lower its freezing point. Of these liquids, however, the first two are easily lost by evaporation. is the duty of a lubricating system to keep a film of clean suitable oil between all metal surfaces which move against each other. Lack of oil will cause friction and abrasion : particles of dirt in the oil will scratch the surfaces and destroy the precise fitting of parts. The film forms only after the engine has been running for a short time, and for this reason the motor should never be raced on starting. There are several different ways of lubricating the engine. In all systems a supply of oil is held in the bottom of the crankcase.
The oil is conducted to the various bearing surfaces by either splash ing, pumping under pressure, or by a combination of both systems.
The oil gauge is the nerve centre of the engine. If the gauge shows no pressure, it is dangerous to drive the machine farther. If the gauge indicates very low pressure, there is good reason to believe that the oil is flowing through the bearings too rapidly. This may mean that the oil is too thin and diluted, or that the bearings are too loose. If the gauge fluctuates, this symptom of distress signifies that there is prob ably not enough oil in the system, that the system is choked or that the pump is in need of repair. In any case, irregularities in the opera tion of the gauge should be taken as the forerunner of trouble and should be investigated immediately. The following are a few rules for
the lubrication of a motor car engine:—(f ) Keep the crankcase filled to the proper level with oil of the grade recommended by a reliable oil company. Do not fill beyond the proper level, as this will make the engine sluggish, and in some cases cause sticking of the valves. (2 ) Change the oil at regular intervals to ensure longer life to the engine. (3) When driving, watch the oil gauge for possible failure in the lub ricating system. (4) Keep the engine clean and inspect the air, fuel and oil cleaners regularly. (5) When the engine is old and bearing and piston fits are loose do not expect heavier oil to correct these defects; have the motor repaired. (6) Do not race a cold engine. (7) Use an oil that will flow freely in winter weather. (8) Do not drive a new auto mobile fast or allow it to become overheated. One quart of light oil per f ogal. of gasoline, poured directly into the fuel tank, may help a great deal during the first few hundred miles of driving a new car. (9) Do not wait until you hear a squeak before lubricating the engine. A squeak means a dry or dirty bearing.