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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 10 (Engine Mechanical - 8.1L) >> Repair Instructions >> Off-Vehicle Repair Instructions >> Piston, Connecting Rod, and Bearings Cleaning and Inspection

Piston, Connecting Rod, and Bearings Cleaning and Inspection

WARNING: This page is about a different variant/trim than selected.
IMPORTANT: The piston diameter can NOT be measured due to the piston coating. Do NOT measure the piston diameter.
IMPORTANT: Measurement of all components should be taken with the components at room temperature.
Do not use a wire brush in order to clean any part of the piston.
    Fig 1: View Of Piston, Connecting Rod & Cap
    GM1486149Courtesy of GENERAL MOTORS CORP.
  1. Clean the piston and pin (144), connecting rod (119) and cap (117) in solvent.
    2. CAUTION: Refer to Safety Glasses Caution in Cautions and Notices.
  2. Dry the components with compressed air.
    3. Fig 2: Cleaning The Piston Ring Grooves With Suitable Ring Groove Cleaning Tool
    GM4977Courtesy of GENERAL MOTORS CORP.
  3. Clean the piston ring grooves with a suitable ring groove cleaning tool.
  4. Clean the piston oil lubrication holes and slots.
    5. Fig 3: View Of Piston Damage
    GM639530Courtesy of GENERAL MOTORS CORP.
  5. Inspect the piston for the following conditions:
    • Eroded areas (1) on the top of the piston
    • Scuffed or damaged skirt (2)
    • Cracks in the piston ring lands, the piston skirt, or the pin bosses
    • Piston ring grooves for nicks, burrs, or other warpage which may cause the piston ring to bind
  6. Inspect the piston pin for scoring, wear or other damage.
    7. Fig 4: Inserting Piston Ring Into Ring Groove
    GM4969Courtesy of GENERAL MOTORS CORP.
  7. Measure the piston ring-to-piston ring groove side clearance. Refer to Engine Mechanical Specifications .
    1. Insert the edge of the piston ring into the piston ring groove.

      Roll the piston ring completely around the piston.

    2. If binding is caused by a distorted piston ring groove, MINOR imperfections may be removed with a fine file.
    3. If binding is caused by a distorted piston ring, replace the piston ring.
    8. Fig 5: Measuring Piston Ring Side Clearance
    GM639528Courtesy of GENERAL MOTORS CORP.
  8. Measure the piston ring side clearance with a feeler gage.
  9. If the side clearance is too small, try another piston ring set. Refer to Engine Mechanical Specifications .
  10. If the proper piston ring-to-piston ring groove clearance cannot be achieved, replace the piston and pin assembly.
    11. Fig 6: View Of Connecting Rod Bearing Bore
    GM639526Courtesy of GENERAL MOTORS CORP.
  11. Inspect the connecting rod for an out-of-round bearing bore.
    12. Fig 7: View Of Twisted Connecting Rod
    GM639524Courtesy of GENERAL MOTORS CORP.
  12. Inspect the connecting rod for twisting.
  13. Inspect the connecting rod for damage to the connecting rod bolt threads.
    14. Fig 8: Measuring Piston Ring End Gap
    GM4968Courtesy of GENERAL MOTORS CORP.
    IMPORTANT: Fit each compression ring to the cylinder in which it will be used.
  14. Measure the piston compression ring end gap.
    1. Place the compression ring into the cylinder bore.
    2. Push the compression ring into the cylinder bore to approximately 6.5 mm (0.25 in) above the ring travel.

      The ring must be square to the cylinder wall.

    3. Use a feeler gage in order to measure the end gap.
    4. Select another size ring set if the end gap exceeds specifications.
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