Crankshaft And Bearings - Cleaning And Inspection: Notes

Tools Required: 

• J 7872  Magnetic Base Dial Indicator Set
• J 8087  Cylinder Bore Gauge

Important:  Use care when handling the crankshaft. Avoid damage to the bearing surfaces or the lobes of the crankshaft position reluctor ring. Damage to the teeth of the crankshaft position reluctor ring may affect OBD II system performance.

1. Clean the crankshaft of the following elements:
   • Oil
   • Sludge
   • Carbon
2. Thoroughly clean all oil passages and inspect for restrictions or burrs.
   CAUTION: Wear safety glasses in order to avoid eye damage.
3. Dry the crankshaft with compressed air.

   Important:  Reluctor ring teeth should not have imperfections on the rising or falling edges.

   Imperfections of the reluctor ring teeth may effect OBD II system performance.

4. Perform a visual inspection of the crankshaft for damage.
   Fig 1: Inspecting Crankshaft For Damage

   Courtesy of GENERAL MOTORS CORP.
5. Inspect the crankshaft journals for wear (1). Journals should be smooth with no signs of scoring, wear, or damage.
6. Inspect the crankshaft journals for grooves or scoring (2).
7. Inspect the crankshaft journals for scratches or wear (3).
8. Inspect the crankshaft journals for pitting or imbedded bearing material (4).
   Fig 2: Inspecting Crankshaft Journals For Wear

   Courtesy of GENERAL MOTORS CORP.
9. Inspect the Woodruff keys (crankshaft balancer) (1), the keyway (2), and the threaded hole (3) for damage.
   Fig 3: Crankshaft Balancer Woodruff Key

   Courtesy of GENERAL MOTORS CORP.
10. Measure the crankshaft journals for out-of-round. Refer to Engine Mechanical Specifications .
11. Measure the crankshaft journals for taper. Refer to Engine Mechanical Specifications .
    Fig 4: Measuring Crankshaft Journals For Taper

    Courtesy of GENERAL MOTORS CORP.
12. Using wooden V blocks, support the crankshaft on the front and rear journals.
13. Use the J 7872  in order to measure the crankshaft runout at the front and rear intermediate journals. Refer to Engine Mechanical Specifications .
14. Use the J 7872  in order to measure the runout of the crankshaft rear flange. Refer to Engine Mechanical Specifications . Replace or repair the crankshaft if the measurements are not within specifications.
    Fig 5: Measuring Runout Of Crankshaft Rear Flange

    Courtesy of GENERAL MOTORS CORP.
15. In order to properly measure the crankshaft end play, the crankshaft, the crankshaft bearings, the crankshaft bearing caps, and the fasteners must be installed into the engine block and the bolts and studs tightened to specifications.
    1. 15.1. Firmly thrust the end of the crankshaft first rearward then forward. This will line up the rear crankshaft bearing and the crankshaft thrust surfaces.
    2. 15.2. With the crankshaft pushed forward, insert a feeler gauge between the crankshaft and the crankshaft bearing surface and then measure the clearance. Refer to Engine Mechanical Specifications .
    3. 15.3. If the correct end play cannot be obtained, verify that the correct size crankshaft bearing has been installed.
    4. 15.4. Inspect the crankshaft for binding. Turn the crankshaft to check for binding. If the crankshaft does not turn freely, loosen the crankshaft bearing bolts and studs, one crankshaft bearing cap at a time, until the tight crankshaft bearing is located.

    Burrs on the crankshaft bearing cap, foreign matter between the crankshaft bearing and the engine block or the crankshaft bearing cap, or a faulty crankshaft bearing could cause a lack of clearance at the crankshaft bearing.

Fig 6: Checking Clearance At Crankshaft Bearing
Courtesy of GENERAL MOTORS CORP.
16. Inspect the crankshaft bearings for craters or pockets. Flattened sections on the crankshaft bearing halves also indicate fatigue.
    Fig 7: Inspecting Crankshaft Bearings For Craters Or Pockets

    Courtesy of GENERAL MOTORS CORP.
17. Inspect the crankshaft bearings for excessive scoring or discoloration.
18. Inspect the crankshaft bearings for dirt or debris imbedded into the crankshaft bearing material.
    Fig 8: Inspect Crankshaft Bearings For Imbedded Dirt Or Debris

    Courtesy of GENERAL MOTORS CORP.
19. Inspect the crankshaft bearings for improper seating indicated by bright, polished sections of the bearing. If the lower half of the bearing is worn or damaged, both the upper and lower halves of the crankshaft bearing should be replaced. Generally, if the lower half of the crankshaft bearing is suitable for use, the upper half of the crankshaft bearing should also be suitable for use.
    Fig 9: Inspecting Crankshaft Bearings For Improper Seating Indicated By Bright, Polished Sections

    Courtesy of GENERAL MOTORS CORP.

    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.

20. Inspect the crankshaft bearing journals and the crankshaft thrust surfaces for the following conditions:
    • Cracks
    • Chips
    • Gouges
    • Roughness
    • Grooves
    • Overheating (discoloration)
21. 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.

22. Inspect the crankshaft bearings for uneven side-to-side wear. This may indicate a bent crankshaft or a tapered bearing journal.
    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.

    Important:  The crankshaft bearings are of the precision insert type. The crankshaft bearings are available in standard and various undersizes.

23. 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.
24. 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 10: Inspecting Thrust Surfaces Of Main Thrust Bearing

    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.

25. Inspect the connecting rod bearing bores or crankshaft main bearing bores using the following procedure:
    1. 25.1. Tighten the bearing cap to specification.
    2. 25.2. Measure the bearing bore for taper and out-of-round using the J 8087  . No taper or out-of-round should exist.
    Fig 11: Inspecting Connecting Rod Bearing Bores Or Crankshaft Main Bearing Bores
    Courtesy of GENERAL MOTORS CORP.