supply houses or manufacturers, these being cut the proper length and not needing any fitting.

Pump Forms and Troubles.-In the water cooling systems which employ a pump to insure positive circulation of the water one may experience cooling troubles if the pump becomes inoperative for any reason. Two forms of circulating pumps are commonly used. That shown at Fig. 172 is a centrifugal form in which the water is circulated by the rotation of a multi-bladed impeller in the casing, and the design outlined at Fig. 173 is a more positive form in which two gears are depended on to keep the water in movement. In the centrifugal form the water enters the pump casing at the center, and is thrown outward by the revolving impeller member, passing out of the case through an outlet pipe attached to the casing. In the gear pump the water enters the casing through either of two openings, and as it cannot pass directly from the inlet to the outlet on account of the tight fit of the gear teeth and of the gears in the casing, the only way it can flow from one side of the case to the other is by filling the tooth spaces of the gears and being carried around from the intake to the discharge opening.

Any condition that would interfere with rotation of the impeller of a centrifugal pump or the gears of a gear pump will interfere with circulation because the water cannot flow by natural means when the system is designed with a view of keeping it in motion by the use of a pump. It is possible for the pump driving means to fail, and in fact on many of the early model cars this was a very common trouble. At the present time water pumps are driven by positive connections with the camshaft, and there is but little opportunity for failure of the driving means. If a pump has been used for a long time the steel shaft on which the impeller is mounted may become rusted enough so that it will be weakened and will rupture. Sometimes the key or pin holding the impeller in place on the shaft will shear off, this being very apt to happen if the pump becomes filled with ice, a not uncommon occurrence in certain sections of this country during the winter season.

The continued rotation of the impeller of a centrifugal pump or the gears of the gear pump may cause wear in the pump casing.

If there is much space between the impeller and the pump casing the efficiency of the pump will be materially reduced. The only remedy for this condition is to replace the worn parts with new. In the centrifugal pump outlined at Fig. 172, which is an accu

rate representation of the device used to circulate water on Packard four and six cylinder cars, it will be noticed that a filter screen is interposed between the intake pipe and the impeller chamber. The function of this screen is to remove all sediment from the cooling water with the object of preventing undue depreciation be

tween the impeller member and the pump casing. In performing this function the screen may become clogged up, and will not permit the water to flow through it as promptly as it should. Provision is made for removing the strainer, and this should be taken out through the opening left after the sediment plug is removed and thoroughly cleaned before it is replaced.

One of the annoying conditions, though not a serious one, that is noticed in a water pump is leakage at various points. It is

evident that there will be an opportunity for water to escape around the driving shaft if the stuffing box is not kept properly screwed up. The stuffing box is provided with a flexible hemp packing which may be compressed tightly against the shaft by screwing down the stuffing box nut and which forms an effective seal against escape of water. The stuffing box packing needs renewal from time to time in order that it may form an effective seal. Other points where a pump may leak are at the packings between the pump case or body and pump cover. If tightening the retaining screws or bolts does not stop the leaking, a new packing must be made to replace the defective one. Pump packings are usually of well shellacked cardboard cut to fit the pump casing

contour and with the screw holes punched through with a belt punch. Sometimes specially prepared rubber packings are used for this purpose.

If the pump is suspected of being defective the following points should be looked at in order: First, the driving means between the pump shaft and the engine; second, the retaining means for driving the impeller of a centrifugal pump or the driven gear of the gear pump; third, the fit between the gears or impeller and the pump casing interior; fourth, the fit between the impeller shaft and its bearings; fifth, the condition of the filter screen or strainer if a member of this nature is interposed between the pump intake and interior. The plunger form of pump, which is widely used in marine service because it is self-priming and must lift water, and the eccentric rotor forms, are seldom used on automobiles. Practically all pumps are either of the centrifugal pattern shown at Fig. 174 or of the gear pattern outlined at Fig. 173.

Methods of Fan Belt Adjustment. If the motor heats up when the engine is running and the car standing still, it is necessary to inspect the fan driving means to make sure that this is functioning properly and that the fan is turning all the time the engine is running. Most fans are flat belt driven, and are mounted on some form of bracket that will permit of maintaining the fan driving belt at the proper tension to insure positive rotation of the fan blades. Some of the most common adjusting means are outlined at Fig. 175. At A the fan is mounted on an extension from an eccentrically mounted piece which may be turned in the clamping support to increase the distance between fan pulley and driving pulley centers. In addition to the eccentric, provision is made for keeping the fan belt at the proper degree of tension by a coil spring attached to a lever fastened to the fan supporting crank at one end and to the supporting bracket at the other. A similar method is shown at B, as the fan shaft is carried at one end of a bell crank which fulcrums on a supporting member in such a way that the tension of the coil spring on the long arm of the bell crank keeps the fan belt tight. At C the fan supporting standard is of tubular form and may be raised or lowered in the socket at its lower end. When the proper degree of ad