As the engine operator, you must constantly be alert to detect any symptoms that might indicate trouble. Such symptoms may be sudden or abnormal changes in the supply, temperature, or pressure of the lubricating oil or cooling water. Color and temperature of the exhaust may also indicate abnormal conditions. Check them frequently. Fuel, oil, and water leaks indicate possible troubles. Keep the engine clean to make such leaks easier to spot.

You will soon become accustomed to the normal sounds and vibrations of a properly operating engine. If you are alert, an abnormal or unexpected change in the pitch or tone of an engines noise or a change in the magnitude or frequency of a vibration will warn you that all is not well. A new sound such as a knock a drop in the fuel injection pressure, or a misfiring cylinder are other trouble warnings for which you should be constantly alert during engine operation.

The following discussion on possible troubles, their causes, and the corrective action necessary is general rather than specific. The information is based on instructions for some of the engines used by the Navy and is typical of most. A few troubles listed may apply to only one model. For specific information on any particular engine, consult the manufacturers technical manual.