Exhaust Manifold Cleaning and Inspection

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 effect On-Board Diagnostics (OBD) II system performance.
• Remove the oxygen sensor prior to cleaning the manifold, do not submerge the oxygen sensor in cleaning solvent.

1. Remove the oxygen sensor from the manifold.
2. Clean the exhaust manifold in solvent.
   CAUTION: Refer to SAFETY GLASSES CAUTION .
3. Dry the exhaust manifold with compressed air.
   Fig 1: Inspecting Exhaust Manifold & Components

   Courtesy of GENERAL MOTORS CORP.
4. Inspect the exhaust manifold air injection reaction (AIR) passages for restrictions.
5. Inspect the AIR flange threaded bolt holes threads for damage.
6. Inspect the AIR flange gasket surface for excessive scratches or gouging.
7. Inspect the exhaust manifold-to-cylinder head gasket surface for excessive scratches or gouging.
8. Inspect for a loose or damaged heat shield.
9. Inspect the take down studs for damaged threads.
   Fig 2: Inspecting Take Down Studs

   Courtesy of GENERAL MOTORS CORP.
10. Using a straight edge and a feeler gage, measure the exhaust manifold cylinder head deck for warpage.

    A exhaust manifold deck with warpage in excess of 0.25 mm (0.01 in), may cause an exhaust leak and may effect OBD II system performance. Exhaust manifolds not within specifications must be replaced.

    Fig 3: Measuring Exhaust Manifold Cylinder Head Deck For Warpage

    Courtesy of GENERAL MOTORS CORP.