GMC Yukon 2000–2006

▸ENGINE1

1. Manufacturer communication2000–2006 GMC YUKON DENALI ・ 2018-09-17(3 earlier editions of this document folded here)

   Engine Block Cylinder Bore Damage Preliminary Information

   1. 1Fault

      • Leak
      • Misfire or rough idle
      • The tip is for cases where cylinder bore damage, scoring or out of round is suspected as the cause of engine oil consumption, misfire, cylinder leakage or blow by.
      ↓→

   2. 2Finding the cause

      • Cylinder: defective
      • Engine Block: defective

      Possible causes

      • Dirt intrusion: if the air filtering system has been compromised the engine wears out very quickly; grit is found in the intake runners and the bores look lightly sand blasted.
      • Catalytic converter failure: if the converter brick is broken, its dust can be drawn back into the engine, and the bores look sand blasted.

      Steps to confirm (in the document’s order)

      1. The peak to valley specification for the crosshatch is .65-2.8 microns.
      2. Cylinder damage or scoring: the cylinder walls have grooves deep enough to catch with a fingernail.
      3. An out of round bore has areas where the crosshatch is missing or worn in different sections of the bore.
      4. If crosshatch is present all the way around the bore from top to bottom, the bore is not out of round.
      ↓→

   3. 3Correction

      Repair

      • With converter dust, the back cylinders go first if caught early; otherwise there is no crosshatch left and the engine needs to be replaced.

      Caution

      • GM has not had an issue with cylinders being machined out of round for any engine family in recent history.
      • A cylinder suspected of being oversize can only be confirmed by checking with an air gauge at the engine plant.
   Read the sentences of the record

   From the manufacturer’s document

   • Applies to：Applies to all brands, models and engines, 2000 - 2019.
   • Condition：The tip is for cases where cylinder bore damage, scoring or out of round is suspected as the cause of engine oil consumption, misfire, cylinder leakage or blow by.
   • Caution：GM has not had an issue with cylinders being machined out of round for any engine family in recent history.
   • Confirm：The peak to valley specification for the crosshatch is .65-2.8 microns.
   • Confirm：Cylinder damage or scoring: the cylinder walls have grooves deep enough to catch with a fingernail.
   • Confirm：An out of round bore has areas where the crosshatch is missing or worn in different sections of the bore.
   • Confirm：If crosshatch is present all the way around the bore from top to bottom, the bore is not out of round.
   • Cause：Dirt intrusion: if the air filtering system has been compromised the engine wears out very quickly; grit is found in the intake runners and the bores look lightly sand blasted.
   • Cause：Catalytic converter failure: if the converter brick is broken, its dust can be drawn back into the engine, and the bores look sand blasted.
   • Repair：With converter dust, the back cylinders go first if caught early; otherwise there is no crosshatch left and the engine needs to be replaced.
   • Caution：A cylinder suspected of being oversize can only be confirmed by checking with an air gauge at the engine plant.

   Open the manufacturer’s document (PDF) ↗ The points above were read from this document.

   Remedy

   This Preliminary Information communication provides information to the technician about engine block of possible cylinder bore damage, scoring or out of round as the possible cause of engine oil consumption, misfire, cylinder leakage or blow by. Technician will need to inspect the engine for Cylinder damage or scoring, An out of round cylinder bore, Dirt intrusion, and Catalytic Converter failure.