Evidence of an unbalanced condition between the cylinders of an engine may be indicated by the following symptoms:

1. Black exhaust smoke. When this occurs, it is not always possible to determine immediately whether the entire engine or just one of the cylinders is overloaded. To determine which cylinder is overloaded, you must open the indicator cock on each individual cylinder and check the color of the exhaust.

2. High exhaust temperatures. If the temperatures of exhaust gases from individual cylinders become higher than normal, it is an indication of an overload within the cylinder. If the temperature of the gases in the exhaust header becomes higher than usual, it is an indication that all cylinders are probably overloaded. Frequent checks on the pyrometer will indicate whether each cylinder is firing properly and carrying its share of the load. Any sudden change in the exhaust temperature of any cylinder should be investigated immediately. The difference in exhaust temperatures between any two cylinders should not exceed the limits prescribed in the engine manufacturers technical manual.

3. High lubricating oil and cooling water temperatures. If the temperature gages for these systems show an abnormal rise in temperature, an overloaded condition may exist. The causes of the abnormal temperature in these systems should be determined and corrected immediately if engine efficiency is to be maintained.

4. Excessive heat. In general, excessive heat in any part of the engine may indicate overloading. An overheated bearing may be the result of an overloaded cylinder; or an abnormally hot crankcase may be the result of overloading the engine as a whole.

5. Excessive vibration or unusual sound. If all cylinders are not developing an equal amount of power, the forces exerted by individual pistons will be unequal. When this occurs, the unequal forces cause an uneven turning movement to be exerted on the crankshaft, and vibrations are set up. Through experience, you will learn to tell by the vibrations and sound of an engine when a poor distribution of load exists. You should use every opportunity to observe and listen to engines running under all conditions of loading and performance.