1978/08/28 Caterpillar


Change In Procedure To Check Main Bearing Clearance{1203}

Usage:


All Engines In All Applications

The Service Manuals and other Caterpillar literature give the procedure to check the clearance between the main bearing journals and main bearings with the crankshaft installed in the engine. In some Service Manuals, part of this procedure is to "Rotate crankshaft one complete revolution with lead wire installed." This instruction is wrong. An accurate check of main bearing clearances can not be made if the crankshaft is rotated (or even moved).

Also, most Service Manuals do not tell you to lift up the crankshaft when the engine is in the normal operating position. Unless the crankshaft is lifted, the lead wire will be made too flat by the weight of the crankshaft and cannot give you a correct measurement of main bearing clearance.

The procedure will be changed when revisions are made to the Service Manuals. This note will be used:

NOTE: When the bearing clearance is checked and the engine is in its normal operating position, such as in the vehicle, the crankshaft will have to be lifted up with a force equal to the weight of the crankshaft and held against the upper halves of the main bearings to get a correct measurement with the wire. The wire will not hold the weight of the crankshaft and give a correct indication. If the engine is in position on its side, such as on an engine stand, it is not necessary to hold the crankshaft up. Do not turn crankshaft when lead wire is in position to check clearance. If lead wire is not available, PLASTIGAGE can be used to check bearing clearance.

Write a note in the Service Manual engine modules in the disassembly and assembly sections under crankshaft that makes reference to this Service Magazine.

Caterpillar Information System:

1978/08/28 A New Ram Support For Use With The Field Service Hose Press{0623}
1978/08/28 Tips For Service Information Retrieval System (SIRS) Users{0374}
1978/08/21 Improved Piston Pins Are Made Of Different Material For Better Hardness Characteristics When Heat Treated{1214}
1978/08/21 Improved Guide Pin For Fuel Injection Pump Lifters{1251}
1978/08/21 Sleeve-Type Ring Compressors Can Be Used For Installation Of Pistons From The Bottom Of The Engine{0622}
1978/08/21 Overlap Joint On Crankshaft Front Seal Ring Prevents Leakage{1160,1202}
1978/08/21 Take Advantage Of The Assembly Procedures And Specifications Charts{0374}
1978/08/07 Remove Fuel Injection Nozzles Before The Bottom Surface Of A Cylinder Head Is Cleaned{1254,1101}
1978/08/07 New Glow Plug Wiring Harness Prevents Short Circuit{1403}
1978/08/07 Four New Contact Points Added To 5P6524 Engine Timing Indicator Group{0653}
1978/07/10 Drill Hole In Handle Of Early 5P3520 Spanner Wrenches For Use With 5P8675 Extension Handle{0620}
1978/07/10 New Flange-Type Seal Used At Rear Of Crankshaft{1161}
1978/08/28 New Design Seals Decrease Shaft Wear In Fuel Transfer Pump{1256}
1978/08/28 New 5P8744 Adapter Assembly And Special Instruction Procedures For 5P4150 Nozzle Tester Group{0650}
1978/08/28 New Oil Supply Line And Gasket For Turbocharger{1307,1052}
1978/08/28 Different O-Ring Seals Now Used In Fuel Injection Pump Group{1251}
1978/09/04 New Camshaft Rear Bearing For The Sleeve Metering Fuel System{1253}
1978/09/04 New Vent Tube For Water Cooled Turbocharger{1380,1052}
1978/09/04 New Torque Specification Used On Bolts That Hold The Cylinder Head{1101}
1978/09/04 Correct Procedure To Adjust Front Power Takeoff Clutches{3055}
1978/09/04 New Gasket Used In Exhaust Manifold Group{1059}
1978/09/04 New Nozzle Assembly Used In Fuel Injection Valves{1254}
1978/09/04 New Water Pump Gives More Pressure{1361}
1978/09/11 New Drive Adapters For Fuel Injection Test Bench{0650}
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