Crankshaft and Bearings Cleaning and Inspection (Bearing Selection): Notes

Tools Required 

• J 36660-A  Torque Angle Meter
• J 8087  Cylinder Bore Gauge

1. Clean the crankshaft of the following elements:
   • Oil
   • Sludge
   • Carbon
2. Inspect the crankshaft oil passages for obstructions.
3. Inspect the crankshaft keyway for nicks or wear.
4. Inspect the crankshaft threads.

   Important:  If cracks, severe gouges or burned spots are found, the crankshaft must be replaced. Slight roughness may be removed with a fine polishing cloth soaked in clean engine oil. Burrs may be removed with a fine oil stone.

   Fig 1: Crankshaft & Bearings

   Courtesy of GENERAL MOTORS CORP.
5. Inspect the crankshaft bearing journals and the crankshaft thrust surfaces for the following conditions:
   • Cracks
   • Chips
   • Gouges
   • Roughness
   • Grooves
   • Overheating (discoloration)
6. Inspect the corresponding crankshaft bearings for embedded foreign material and determine the source.

   Important:  Note the location of the crankshaft main bearing high spots. If they are not in line, the crankshaft is bent and must be replaced.

7. Inspect the crankshaft bearings for uneven side-to-side wear. This may indicate a bent crankshaft or a tapered bearing journal.
8. The crankshaft bearings are of the precision insert type. The crankshaft bearings are available in standard and various undersizes.
   NOTE: Do not scrape, shim, or file bearing inserts. If the bearing surface of the insert is touched with bare fingers, the skin oil and acids will etch the bearing surface.
9. Inspect the outer surfaces of the crankshaft bearings for the following conditions:
   • Wear - surface wear indicates either movement of the insert or high spots in the surrounding material (spot wear).
   • Overheating or discoloration
   • Looseness or rotation indicated by flattened tangs and wear grooves
10. Inspect the thrust surfaces of the main thrust bearing for the following conditions:
    • Wear
    • Grooving (Grooves are caused by irregularities of the crankshaft thrust surface.)
    Fig 2: Crankshaft Bearings

    Courtesy of GENERAL MOTORS CORP.

    Important:  If crankshaft bearing failure is due to other than normal wear, investigate the cause. Inspect the crankshaft or connecting rod bearing bores.

11. Inspect the connecting rod bearing bores or crankshaft main bearing bores using the following procedure:
    1. 11.1. Tighten the bearing cap to specification.
    2. 11.2. Measure the bearing bore for taper and out-of-round using the J 8087  . No taper or out-of-round should exist.
    Fig 3: Measuring Bearing Bore Using J 8087

    Courtesy of GENERAL MOTORS CORP.