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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 719 (ENGINE MECHANICAL - 8.1L (UNIT REPAIR))REPAIR INSTRUCTIONSENGINE BLOCK CLEANING AND INSPECTION
2003 Chevrolet TrailBlazer 4.2 S, 4WD

Engine Block Cleaning and Inspection

2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Engine Block Cleaning and Inspection
WARNING: This page is about a different car, the 2002 GMC Yukon XL, 2002 Chevrolet Suburban, and 2002 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.
  1. Boil the cylinder block in caustic solution.
  2. Flush the cylinder block with clean water or steam.
  3. Clean the following areas:
    • All gasket surfaces; Refer to Replacing Engine Gaskets .
    • Cylinder bores, remove excessive cylinder ring ridge as required
    • Main bearing caps
    • Oil galleries, remove all sludge or restrictions
    • Scale deposits from the coolant passages
    • All dirt or debris from threaded bolt holes
      Fig 1: Engine Block Inspection Areas
      G01675413Courtesy of GENERAL MOTORS CORP.
    CAUTION: Refer to SAFETY GLASSES CAUTION in Cautions and Notices.
  4. Dry the block with compressed air.
  5. Lubricate the cylinder bores with clean engine oil to prevent rusting.
  6. Inspect the engine block for the following conditions:
    • Gasket surfaces for deep gouges or other damage
    • Crankshaft bearing bores for wear
      • The surfaces where the crankshaft bearings contact the crankshaft bearing bore must be smooth.
      • All crankshaft bearing bores must be round and uniform in inside diameter (ID) at all the bearing supports.
      • If a crankshaft bearing cap is damaged and requires replacement, refer to Crankshaft and Bearings Cleaning and Inspection .
    • Camshaft bearing bores for wear or damage
    • Valve lifter bores for scuffing or wear
    • Engine block for cracks or other damage
    • Cylinder walls for scoring or gouges
    • Coolant jackets for cracks
    • Crankshaft bearing webs for cracks
    • Engine mount bosses for damage
    • The oil passages for restrictions
  7. Inspect the engine block cylinder head deck for flatness using a straight edge and a feeler gage.

    The surface must be flat within 0.100 mm (0.004 in).

    Fig 2: Inspecting Engine Block Head Deck For Flatness
    G01675414Courtesy of GENERAL MOTORS CORP.
  8. Use a bore gage and measure the cylinder bore for taper, out-of-round and oversize. Slide the bore gage up and down throughout the length of the cylinder bore. Check the bore both parallel and perpendicular to the centerline of the crankshaft at the top, center and bottom of the bore. A cylinder bore that measures 107. 940-107.990 mm (4.249-4.251 in) may be serviced with a standard size piston/connecting rod assembly. A cylinder bore that exceeds the maximum diameter must be serviced with an oversized piston/connecting rod assembly.
    Fig 3: Measuring Cylinder Bore
    G01675415Courtesy of GENERAL MOTORS CORP.
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.