Crankshaft Bearing Inspection

Crankshaft Bearing Inspection






1. Important:
^ All connecting rod and main journal bearings that have been used in a running engine must be replaced. Never re-use the crankshaft or connecting rod bearings.
^ The following bearing wear conditions should be used to diagnose engine operating conditions or root cause of a condition.
Inspect for fatigue indicated by craters or pockets. Flattened sections on the bearing halves also indicate fatigue.





2. Inspect for excessive scoring or discoloration on both front and back of the bearing halves.
3. Inspect the main bearings for dirt embedded into the bearing material.





4. Inspect for improper seating indicated by bright, polished sections.

Crankshaft Measurement

Tools Required
^ J7872 Magnetic Base Dial Indicator





1. Using a suitable fixture, support the crankshaft.





2. Install the J7872.
3. Measure the crankshaft runout using the J7872. Refer to Engine Mechanical Specifications.





4. Measure the crankshaft thrust wall width (1) for wear using an inside micrometer. Refer to Engine Mechanical Specifications.
5. Measure the crankshaft thrust wall surface (2) for runout using the J7872. Refer to Engine Mechanical Specifications.
6. If the crankshaft journals are damaged or worn beyond specifications, the crankshaft may be ground 0.25 mm (0.010 inch). There is only 1 size of oversized main bearings available for service.





7. Inspect the crankshaft main journals for undersize, using an outside micrometer.





8. Inspect the crankpins for undersize using an outside micrometer.
9. Compare your measurements with those listed in the Engine Mechanical Specifications. If the crankpin journals are worn beyond the specifications, the crankshaft may be ground 0.25 mm (0.010 inch). There is only 1 size of oversized connecting rod bearings available for service.





10. Measure the main bearing and crankpin journals for out-of-round using the following procedure:
1. Using an outside micrometer, measure the journal at the extreme front and rear locations on the journal. Call these points A and B.
2. Measure the journal in 2 new locations exactly 90 degrees from the first points. Call these points C and D.
3. Subtract A from C and B from D. The differences will indicate journal out-of-round.
4. The out-of-round should not exceed 0.004 mm (0.00016 inch) maximum.
5. If the journals are worn beyond the specifications, the crankshaft may be ground 0.25 mm (0.010 inch). There is only 1 size of oversized crankshaft and connecting rod bearings available for service.
11. Measure the main bearing and crankpin journals for taper using the following procedure:
1. Using an outside micrometer, measure the journal at the extreme front (A) and rear (B) of the journal parallel to the crankshaft centerline.
2. Subtract the smallest from the largest measurement. The result will be the journal taper.
3. If the main bearing journal taper exceeds 0.004 mm (0.00016 inch), replace the crankshaft.
4. If the journals are worn beyond the specifications, the crankshaft may be ground 0.25 mm (0.010 inch). There is only 1 size of oversized crankshaft and connecting rod bearings available for service.