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Crankshaft And Main Bearings

WARNING: This page is about a different car, the 2002 Pontiac Firebird and 2002 Chevrolet Camaro. However, it is still accessible from the selected car via links, so may be relevant.
CAUTION: 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 effect On-Board Diagnostics (OBD) II system performance.
NOTE: 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.
NOTE: 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 OBD II system operation.
NOTE: Prior to main bearing cap removal, note installed direction and location for installation reference.
  1. Clean the crankshaft with solvent. Thoroughly clean all oil passages and inspect for restrictions or burrs. Dry the crankshaft with compressed air.
    2. NOTE: The 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.
  2. Perform a visual inspection of the crankshaft for damage. Inspect the crankshaft position reluctor ring lobes for damage.
  3. Inspect the crankshaft journals for wear. Journals should be smooth with no signs of scoring, wear, or damage. Inspect the crankshaft journals for grooves or scoring. Inspect the crankshaft journals for scratches or wear. Inspect the crankshaft journals for pitting or imbedded bearing material.
  4. Inspect the crankshaft key, keyway, and threaded hole for damage. Measure the crankpins for the out-of-round. Measure the crankpins for taper. See CRANKSHAFT, MAIN & CONNECTING ROD BEARINGS SPECIFICATIONS  table.
  5. Measure the crankshaft thrust wall width. See CRANKSHAFT, MAIN & CONNECTING ROD BEARINGS SPECIFICATIONS  table. A crankshaft with a thrust wall width in excess must be replaced.
  6. Measure the crankshaft runout. Use wooden "V" blocks or a fixture to support the crankshaft on the front and rear journals.
  7. Use the Magnetic Dial Indicator (J-7872), in order to measure the crankshaft runout at the front and rear intermediate journals. Use the dial indicator in order to measure the runout of the crankshaft rear flange. Use the dial indicator in order to measure the runout of the crankshaft position reluctor ring.
  8. Reluctor ring runout should be measured 0.04" (1.0 mm), below the ring teeth. If the reluctor ring has runout in excess, replace the crankshaft. See CRANKSHAFT, MAIN & CONNECTING ROD BEARINGS SPECIFICATIONS  table.
    9. NOTE: A loose or damaged crankshaft oil gallery plug must be replaced.
  9. Inspect the crankshaft rear oil gallery plug for a loose fit or leaking. See Fig 1.
  10. Inspect crankshaft bearings for craters or pockets. Flattened sections on the bearing halves also indicate fatigue. Inspect the crankshaft bearings for excessive scoring or discoloration. Inspect the crankshaft bearings for dirt or debris imbedded into the bearing material.
  11. 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 upper and lower halves should be replaced. Generally, if the lower half is suitable for use, the upper half should also be suitable for use.
  12. To measure main bearing clearance, remove the bearing cap M8 side bolts. Remove the bearing cap M10 bolts and studs.
  13. Install the Crankshaft Bearing Cap Remover (J-41818) to the bearing cap. See Fig 2. Tighten the bearing cap remover bolts to specification. See TORQUE SPECIFICATIONS .
  14. Install the Slide Hammer (J-6125-1B) to the bearing cap remover in order to remove the bearing cap. Remove the bearing cap and lower bearing. Install gauging plastic onto the crankshaft journal. Install the gauging plastic the full width of crankshaft bearing journal.
  15. Install the bearing, bearing cap, bolts and studs. Tighten the inner bolts first then the outer studs to specification. See TORQUE SPECIFICATIONS .
  16. Tighten the side cap bolts to specification. See TORQUE SPECIFICATIONS . Tighten the bolt on one side of the bearing cap and then tighten the bolt on the opposite side of the same bearing cap. See Figure.
  17. Remove the bearing cap M8 side bolts. Remove the bearing cap bolts and studs. Use the bearing cap remover and the slide hammer in order to remove the bearing cap.
  18. Measure the gauging plastic at its widest area using the scale supplied with the plastic gauging kit.
    • If the gauging plastic shows irregularity in the journal exceeding 0.001" (0.025 mm), remove the crankshaft and measure the journal with a micrometer.
    • If the bearing clearance is greater than wear limit, select and install an undersized bearing set, and measure the clearance with gauging plastic. See CRANKSHAFT, MAIN & CONNECTING ROD BEARINGS SPECIFICATIONS  table.
    • If clearance cannot be brought to specifications, replace the crankshaft or grind the crankshaft for use with the next undersized bearing.
  19. Measure the crankshaft end play. Thrust the crankshaft forward or rearward and insert a feeler gauge between the center crankshaft bearing and the bearing surface of the crankshaft and measure the bearing clearance. See CRANKSHAFT, MAIN & CONNECTING ROD BEARINGS SPECIFICATIONS  table.
  20. 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. If bearing surface is okay, 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.
  21. To measure connecting rod bearing clearance, remove the bearing cap, bearing half and bolts.
  22. Install the gauging plastic onto the connecting rod bearing journal. Install the gauging plastic the full width of the journal. Install the bearing cap, bearing, and bolts. Tighten the connecting rod bolts to specification. See TORQUE SPECIFICATIONS .
  23. Measure the gauging plastic at its widest area using the scale supplied with the plastic gauging kit. See CRANKSHAFT, MAIN & CONNECTING ROD BEARINGS SPECIFICATIONS  table.
Fig 1: Inspecting Crankshaft Oil Gallery Plug
G00081717Courtesy of GENERAL MOTORS CORP.
Fig 2: Removing Crankshaft Bearing Caps
G00081718Courtesy of GENERAL MOTORS CORP.
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