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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 992 (Engine Mechanical - 4.3L) >> 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 car, the 2004 GMC Sierra and 2004 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
    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.
  1. Clean the piston and connecting rod in solvent.
    2. Fig 1: Piston & Connecting Rod Components
    GM34671Courtesy of GENERAL MOTORS CORP.
    CAUTION: Refer to Safety Glasses Caution in Cautions and Notices.
  2. Dry the components with compressed air.
  3. Clean the piston ring grooves with a suitable ring groove cleaning tool.
    4. Fig 2: Cleaning The Piston Ring Grooves With Suitable Ring Groove Cleaning Tool
    GM4977Courtesy of GENERAL MOTORS CORP.
  4. Clean the piston oil lubrication holes and slots.
  5. Inspect the piston for the following:
    • Eroded areas (1) on the top of the piston
    • Scuffed or damaged skirt (2)
    • Damage to the pin bore (3)
    • 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. Fig 3: Identifying Piston Damage Inspection Areas
    GM156168Courtesy of GENERAL MOTORS CORP.
  6. Inspect the piston pin for scoring, wear or other damage.
  7. Measure the piston ring-to-piston ring groove side clearance.
    1. Insert the edge of the piston ring into the piston ring groove.
    2. Roll the piston ring completely around the piston.
      • If binding is caused by a distorted piston ring groove, MINOR imperfections may be removed with a fine file.
      • If binding is caused by a distorted piston ring, replace the piston ring.
    8. Fig 4: Inserting Piston Ring Into Ring Groove
    GM4969Courtesy of GENERAL MOTORS CORP.
  8. Measure the piston ring side clearance with a feeler gauge.
    9. Fig 5: Measuring Piston Ring Side Clearance
    GM22934Courtesy of GENERAL MOTORS CORP.
  9. If the side clearance is too small, try another piston ring set.
  10. If the proper piston ring-to-piston ring groove clearance cannot be achieved, replace the piston and pin assembly.
  11. To determine the proper piston ring side clearance, refer to Engine Mechanical Specifications .
  12. Inspect the connecting rod for an out-of-round bearing bore. Refer to Engine Mechanical Specifications .
    13. Fig 6: View Of Connecting Rod
    GM156167Courtesy of GENERAL MOTORS CORP.
  13. Inspect the connecting rod for twisting.
    14. Fig 7: Identifying Twisted Connecting Rod
    GM156169Courtesy of GENERAL MOTORS CORP.
  14. Inspect the connecting rod for damage to the bearing cap and bolt threads.
  15. Measure the piston compression ring end gap.
      IMPORTANT: Fit each compression ring to the cylinder in which it will be used.
    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. Refer to Engine Mechanical Specifications .
    16. Fig 8: Measuring Piston Ring End Gap
    GM4968Courtesy of GENERAL MOTORS CORP.
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