Measuring Main Bearing Clearance - Gaging Plastic Method

Important:  The crankshaft main bearings are a precision insert type. Main bearing caps are machined with the engine block for proper clearance and cannot be shimmed or filed for bearing fit. If the clearances are found to be excessive, new bearings and/or engine block and cap repair or replacement may be required.

Do not rotate the crankshaft while gauging plastic is between the crankshaft journal and the bearing surface.

The crankshaft bearing clearances are critical.

Excessive bearing clearance may effect crankshaft position sensor signals and may effect On-Board Diagnostics (OBD) II system operation.

Important:  Remove the bearing cap side bolts prior to cap removal.

1. Remove the bearing cap M8 side bolts.
   Fig 1: Removing Bearing Cap M8 Side Bolts

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2. Remove the bearing cap M10 bolts and studs.
   Fig 2: Removing Bearing Cap M10 Bolts And Studs

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   NOTE: Refer to FASTENER NOTICE .
3. Install the J 41818  to the bearing cap.

   Tighten 

   Tighten the J 41818  bolts to 11 N.m (100 lb in).

4. Install the J 6125-1B  to the J 41818  in order to remove the bearing cap.
   Fig 3: Installing J 6125-1B To J 41818 To Remove Bearing Cap

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5. Remove the bearing cap and lower bearing.
   Fig 4: Removing Bearing Cap And Lower Bearing

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6. Install gaging plastic onto the crankshaft journal.

   Install the gaging plastic the full width of crankshaft bearing journal.

   Fig 5: Installing Gaging Plastic Onto Crankshaft Journal

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7. Install the bearing, bearing cap, bolts and studs.
   Fig 6: Identifying Bolt & Stud Tightening Sequence

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   Tighten 

   1. 7.1. Tighten the inner bolts (1-10) a first pass in sequence to 20 N.m (15 lb ft).
   2. 7.2. Tighten the inner bolts (1-10) a final pass in sequence to 80 degrees using the J 36660-A  .
   3. 7.3. Tighten the outer studs (11-20) a first pass in sequence to 20 N.m (15 lb ft).
   4. 7.4. Tighten the outer studs (11-20) a final pass in sequence to 53 degrees using the J 36660-A  .
   5. 7.5. Tighten the side cap bolts to 25 N.m (18 lb ft).

      Tighten the bolt on one side of the bearing cap and then tighten the bolt on the opposite side of the same bearing cap.

   Important:  Remove the bearing cap side bolts prior to cap removal.

8. Remove the bearing cap M8 side bolts.
   Fig 7: Removing Bearing Cap M8 Side Bolts

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9. Remove the bearing cap bolts and studs.
   Fig 8: Removing Bearing Cap Bolts And Studs

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10. Use the J 41818  and the J 6125-1B  in order to remove the bearing cap.
    Fig 9: Removing Bearing Cap

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11. Measure the gaging plastic at its widest area using the scale supplied with the plastic gaging kit.
    Fig 10: Measuring Gaging Plastic At Its Widest Area

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    • If the gaging plastic shows irregularity in the journal exceeding 0.025 mm (0.001 in), remove the crankshaft and measure the journal with a micrometer.
    • If the bearing clearance is greater than 0.065 mm (0.0025 in), select and install an undersized bearing set, and measure the clearance with gaging plastic.
    • If clearance cannot be brought to specifications, replace the crankshaft or grind the crankshaft for use with the next undersized bearing.
12. Measure the crankshaft end play.
    Fig 11: Measuring Crankshaft End Play

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    1. 12.1. Thrust the crankshaft forward or rearward.
    2. 12.2. Insert a feeler gage between the center crankshaft bearing and the bearing surface of the crankshaft and measure the bearing clearance. Refer to ENGINE MECHANICAL SPECIFICATIONS - LS1  or ENGINE MECHANICAL SPECIFICATIONS - LS6 .
    3. 12.3. If the bearing clearance is not within specifications:
       • Inspect the thrust surfaces for nicks, gouges or raised metal. Minor imperfections may be removed with a fine stone.
       • Replace the thrust bearings and measure the end play.
       • If the correct measurements cannot be obtained, repair the crankshaft thrust surfaces or replace the crankshaft.