To ensure that all the parts of an engine receive adequate lubrication, it is essential that all parts of the lubricating oil system be properly main-tained at all times. Some parts which may be a source of trouble are considered in this section. For other information on lubricating systems, see Engineman 3 & 2, NAVEDTRA 10541 (current edition).

LUBE OIL PUMPS

Pumps used in engine lubricating systems are of the positive displacement type. In some pumps pressure control is maintained by pressure regulating or pressure relief valves built directly into the pump; in other pumps, valves exterior to the pump are used for this purpose. Most regulating devices recirculate excess lube oil back to the suction side of the pump, but some pumps discharge excess oil directly into the engine sump. Pump casualties, as well as many other lube systems failures, are indicated by the loss of lube oil pressure. The loss of oil pressure can be recognized by checking the pressure gages at prescribed intervals, or by means of an electrical alarm system. Most lube oil pump failures are generally due to wear, and develop gradually. Failures may also occur abruptly if a drive shaft breaks, or some parts suffer physical deformation. Such failures are usually indicated by ab-normal noise in the pump and by sounding of the low-pressure lube oil alarm.

The warning system should be tested at specified intervals, usually when an engine is being started or secured. Warning systems do not excuse personnel from their responsibility for keeping a vigilant and accurate watch on engine instruments. The instruments give the most reliable indication as to what an engine is doing and what adjustments should be made.

OIL LINES AND PASSAGES

Troubles occurring in the oil passages and oil lines are usually in the form of plugged or cracked lines. The former is generally the result of carelessness, while the latter is usually a result of improper support of the line.

Even though clogged passages may be indicated by increased pressure gage readings, it is dangerous to rely wholly on such indications, since stoppage occurring beyond the pressure regulating valve and pressure gage may cause very little, if any, pressure increase on the gage. You can best determine if a bearing is receiving oil by inspecting it occasionally, just after engine shut-down. There should be plenty of oil in the vicinity of the parts being lubricated. Another method for checking bearing lubrication is to note the temperature of the bearings by feeling them with the hand after engine shut-down. You should be able to keep your hand on them for at least a few seconds.

You can help prevent most oil line stoppage by observing the following rules:

1. Never use cotton waste or paper towels for cleaning an engine. They may leave lint or small bits of material which later may collect in the lines.

2. Service the oil filters at specified intervals. Clean the case properly and when the lines are removed, blow them out with compressed air.