GM Service Manual Online
For 1990-2009 cars only

    Object Number: 1277089  Size: SH

    Important: Do not use the exhaust manifold-to-cylinder head gaskets again. Upon installation of the exhaust manifold, install a NEW gasket. An improperly installed gasket or leaking exhaust system may affect on-board diagnostics (OBD) II system performance.

  1. Clean the exhaust manifold (600) and heat shield (603) in solvent.
  2. Dry the exhaust manifold with compressed air.
  3. Inspect the exhaust manifold-to-cylinder head gasket surface for excessive scratches or gouging.
  4. Inspect for a loose or damaged heat shield (603).
  5. Inspect the exhaust pipe studs for damaged threads.

  6. Object Number: 66607  Size: SH
  7. Use a straight edge and a feeler gage and measure the exhaust manifold cylinder head deck for warpage.
  8. An exhaust manifold deck with warpage in excess of 0.25 mm (0.01 in) within the 2 front or 2 rear runners or 0.5 mm (0.02 in) overall, may cause an exhaust leak and may affect OBD II system performance. Exhaust manifolds not within specifications must be replaced.