Fig. 47. Thermo-Syphon Cooling System
[Fig. 47] shows how the water circulates in the Thermo-Syphon system. It acts on the principle that hot water seeks a higher level than cold water, consequently when the water reaches a certain temperature, approximately 180° F., circulation commences and the water flows from the lowest radiator outlet pipe up through the water jackets into the upper radiator water tank, and down through the thin tubes to the lower tank to repeat the process.
The heat is extracted from the water by its passage through the thin metal tubing of the radiator to which are attached scientifically worked out fins which assist in the rapid radiation of the heat. The fan just back of the radiator sucks the air through the small tubes which connect the upper and lower radiator tanks. The air is also driven through between these tubes by the forward movement of the car.
The Force Pump Circulation System.—The Force Pump circulating system is constructed in the same manner as the Thermo Syphon Cooling System. The only difference in the two systems is that a small pump is attached to the lower radiator pipe to force the circulation of the water.
The pump is usually of the centrifugal type and consists of a fan-shaped wheel operated in a snugly fitted housing. The water enters at the hub and is thrown out against the housing and is forced on by the rapid action of the fan blades. Another type of pump is used by some manufacturers which consist of two meshed gears of the same size, which operate in a snugly fitted housing. These gears operate in a direction toward each other, the water is carried forward or upward in the space between the teeth, and is forced on when the teeth mesh and fill the space.
Overheating.—Overheating may be caused by carbonized cylinders, too much driving on low speed, not enough or a poor grade of lubricating oil, spark retarded too far, racing the engine, clogged muffler, poor carburetor adjustment, a broken or slipping fan belt, jammed radiator tube, leaky connection, or low water.
Radiator Cleaning.—The entire circulation system should be thoroughly cleaned occasionally. A good cleaning solution is made by dissolving one-half pound of baking soda in three and one-half to four gallons of soft water. The radiator is filled with the solution and left to stand for twenty to thirty minutes. The hose is then removed from the lower pipe, water is then turned into the radiator through the filler spout until the system is thoroughly flushed out.
Freezing.—Unless an anti-freezing solution is used through the cold months you are bound to experience trouble. The circulation does not commence properly until the water becomes heated. It is apt to freeze at low temperatures before circulation commences. In case any of the small tubes are plugged or jammed they are bound to freeze and burst open if the driver attempts to get along without a non-freezing solution.
Freezing Solution.—Wood or denatured alcohol can be used to a good advantage. The following table gives the freezing point of solutions containing different percentages of alcohol.
20% solution freezes at 15° above zero.
30% solution freezes at 8° below zero.
50% solution freezes at 34° below zero.