thus preventing leakage of water without undue pressure on the pump shaft.

After a new car has been run a thousand miles the stuffing box nut on each side of the pump should be tightened a trifle. Cooling of the water through the radiator is aided by means of a fourblade fan set on the front end of the motor and driven by means of a "V" belt from the pump shaft. If the leather belt on the

Parts.

fan stretches from considerable use, it may be tightened by loosening the stud on the fan bracket and raising the fan enough to remove the slack from the belt.

Deposits in Radiator and Piping.-The form of radiator most generally used at the present time has a number of very narrow tortuous passages through which the water must pass in going from the upper compartment where it is discharged after leaving the motor cylinders, to the lower compartment where it collects after being cooled and from which it is drawn by the circulating

pump. The water used in some localities for cooling contains much matter either in suspension or solution which will form scale or a powdery deposit in the radiator tubes. It does not take much scale to seriously reduce the ratio of heat conduction between the heated water inside of the tube and the cooling air currents which

Fig. 171.-The Packard Cooling System, Showing All Important Components.

are circulated about their exterior. As cylinders are generally of east iron, a certain amount of rust will be present in the water jacket, and this also may get into the radiator piping. If an antifreezing solution using some salt as a basis such as calcium-chloride is employed, after this has been circulated through the radiator and piping for a time it may deposit solid matter in the form of crystals in the piping or radiator. Anti-freezing solutions that include glycerine may have a chemical action due to the acid sometimes found in the cheap commercial grades of glycerine employed for this purpose. This chemical action results in the deterioration of the water jacket walls, and also contributes to the rust deposit.

Cleaning Sand from Water Jackets.-In some cases excessive heating of an engine has been found to be due to a retention of part of the sand core in the water jacket of the cylinder casting. This is very apt to be the case if the casting is in such form that the water jacket interior is inaccessible. On those types of unit castings where a large side plate is employed to close an opening that occupies practically the entire side of a water jacket, no difficulty obtains in cleaning out all core sand, but where this precaution is not taken and the core supported by prints of small size, there is considerable difficulty in clearing the casting in some cases. For those not familiar with foundry practice the writer may say that the core is that portion which is used in the mold to represent the space between the cylinder wall and water jacket, as it is necessary to use some such filler in the mold when pouring the molten metal into the impression left by the pattern to form the cylinder. Cores are usually made of fine sand held together by binding material, and in some cases with pieces of wire running through as a re-enforcement, the whole being baked to form one piece before it is placed in the mold. A piece of this core may become lodged in some angle or corner and remain there even though the greater portion of the core is removed by the foundryman. This may not become loose until the engine has been in use for some time, and then it may be carried into a pipe or opening and partially or wholly interrupt the water circulation. The piece of core may dissolve and deposit considerable sand in the water jacket which will collect in some corner where it may affect circulation. In order to remove all traces of sand, where mechanical means are not practical, an authority recommends a solution of hydrofluoric acid and water, the proportions being about one part acid to ten of water. This should be poured into the jacket and allowed to stand over night, which will loosen the sand or dissolve it. The cylinder jacket should be thoroughly drained and all traces of the acid removed by flushing thoroughly with hot water under pressure. Hydrofluoric acid is the only one that will attack sand, and it is well to remember that it has the same effect on glass which is usually indifferent to the action of the other common acids. Care must be taken, therefore, to keep it in the

special rubber container, in which it is received from the chemical supply house. While this chemical will also attack the metal of which the cylinder is composed, the diluted solution recommended will have no material effect in the short time required to thoroughly dissolve the sand.

It is not advisable to use the diluted acid in the water spaces of the radiator, as the brass or copper used in this part of the cooling system is much thinner than the material employed in the water jacket, and is also more easily attacked by the acid. For cleaning out the water spaces of a radiator a solution of potash or washing soda may be used. This will cut the rust and some forms of scale and will dissolve them or loosen them sufficiently so the deposits may be thoroughly flushed out with water or steam under pressure. The solution will work more rapidly if it is brought to the boiling point before placing it in the radiator. The potash solution is also valuable in removing rust from the water jacket interior.

Incrustation is most commonly caused by carbonate of lime which is held in solution in some water as a bicarbonate; therefore, when the water is heated the carbonic acid is driven off and the carbonate is precipitated in the form of a muddy deposit which hardens in the presence of heat into a nonconducting scale in those portions of the water jacket where the heat is greatest, and which remains in the form of a powdery deposit in the radiator tubes where the heat is not great enough to harden the sediment. Sometimes the deposit is sulphate of lime, this also being found in the water available in some localities. The reason that water contains so many impurities is because it is one of the best known solvents. Pure water is never found in nature and can only be obtained by a process of distillation. The purest natural water is rain, and if this is collected before it touches the earth it contains only such impurities as may be derived from the atmosphere, these consisting of gases in the open country such as nitrogen and carbon dioxide. That falling over towns absorbs quantities of acids and· soluble salts. Rain water collected near the ocean contains chlorine. The source of water supply in many communities is some river flowing through or within a short distance. A large variety