| Cause | 4. Water entering cylinder. | very unusual. |
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5. Too powerful a charge. | |
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6. Incrustation of jackets. |
Cause 1. Water Circulation Stopped.—Of these the cessation of water circulation for cooling is the most important. It must be the result (a) of the pump ceasing to act through bad adjustment of its driving-gear, or through its valves or cogs jamming; its spindle being seized or bent; the interior fan worn or unkeyed; the friction wheel unkeyed, or its tyre worn out or come off.
As regards the adjustment of the driving-gear of a centrifugal pump driven by friction, the friction wheel and spindle should revolve freely when the pump is pulled away from the fly-wheel. It should be adjusted so that the spring presses it lightly but firmly against the fly-wheel; cafe should also be taken in packing the glands of these pumps, for they run at a very high velocity; a very slight leak of water, however, is advantageous for lubrication.
(b) The blockage of a water-pipe or passage will also impede the circulation, or
(c) There may be an air or steam lock in the pipes. The best way of getting rid of an air lock is to open all cocks and plugs in the water system and run the engine, filling up the tank and water jackets to make up what is running out. This will eventually expel any air, and the water will circulate freely.
Cause 2. Water Lost.—If all the water has been lost on the road through the breakage of a pipe or the opening of a plug or tap, or loosening of a joint, and no water is near, you can continue your journey spasmodically by allowing the engine to cool down, then run on a mile or two with the bonnet open or off until it shows symptoms of overheating again, when stop, paraffin your cylinders, and wait another half-hour. The pump of a car has several times been known to have been carried away by contact with a dog; in one case there was no trace of pump or dog except a tooth which the unfortunate animal left in the back tyre.
Note.—Always carry rubber tubing to repair ruptured pipes.
Cause 3.—If the overheating has been caused by fan It v lubrication, it is probable that this is due to inattention to the lubricators.
Remarks as to Lubrication.—It should be ascertained from the makers how many drops a minute are required for the proper
