a feeler gauge between the ring and the side of the ring groove, as shown in figure 3-37. Check the manufacturer's repair manual for proper clearance. If it is excessive, the piston should be replaced.

OPERATIONAL TESTING

Large engines are expensive items. Repairs, as evidenced by the preceding overhaul procedures, are costly and time consuming. Because of this, to get the most out of the newly overhauled engine, use proper initial start-up and run-in procedures.

PRESTART-UP

Normally, the engine will be set in its own mountings in a piece of CESE. For this reason, more than just engine connections are involved, First, check the level of all of the fluids: coolant, oil, hydraulic, and fuel. Then check things like electrical hookups, mechanical linkage, and cable connections. Recheck all mounting bolts, and be sure that all drive belts are in place and tight. Be sure that there are no loose items lying around that can get caught in the running gear.

WARNING ENSURE THAT ANY EMERGENCY SHUT-DOWN SYSTEMS ARE OPERATIONAL.

Figure 3-37. - Checking ring groove side clearance.

INITIAL START-UP AND RUN-IN

Upon starting the newly overhauled engine, if no oil pressure is observed in the first 10 to 15 seconds, shut the engine down and find the cause. If oil pressure is observed, allow the engine to warm up at an idle. Do NOT load the engine before it is fully warmed up. During this warm-up period, check for any leaks and listen for any abnormal noises that could indicate trouble. After the warm-up period, shut the engine down and check all fluid levels, repair any leaks, and retorque any bolts, as required.

500-MILE/50-HOUR CHECK

The most probable time for a newly overhauled engine to malfunction is during its initial run-in and break-in period. Therefore, it is absolutely necessary that when these units are returned to service, they are done so with special instructions to the dispatcher and yard boss; for instance, only light loads for the first 500 miles/50 hours, and watch all fluid levels, temperatures, and pressures carefully. Last, ensure that the unit is brought into the shop after the break-in period for an oil and filter change. The unit is now ready for full service.

REFERENCES

Crouse, William H. and William L. Anglin, Automotive Mechanics, 9th ed., Gregg Division, McGraw-Hill Book Company, New York, 1985.

Detroit Diesel Engines V-71 Service Manual, Detroit Diesel Allison, 13400 West Outer Drive, General Motors Corporation, Detroit, 1982.

U.S. Department of Defense, Principles of Automotive Vehicles, TM-9-8000, Head- quarters, Department of the Army, Washington D.C., October, 1985.