Exhaust Manifold Cleaning and Inspection

Important: 

• Do not reuse the exhaust manifold-to-cylinder head gaskets. Upon installation of the exhaust manifold, install a NEW gasket. An improperly installed gasket or leaking exhaust system may effect On-Board Diagnostic (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.
3. Dry the exhaust manifold with compressed air.
4. Inspect the heat shield for damage.
   Fig 1: Inspecting Exhaust Manifold & Heat Shield

   Courtesy of GENERAL MOTORS CORP.
5. Use a straight edge and a feeler gage and measure the exhaust manifold mounting face for warpage.

   An exhaust manifold face with warpage in excess of 0.25 mm (0.010 in) may cause an exhaust leak and may effect OBD If system performance. Exhaust manifolds not within specifications must be replaced.

   Fig 2: Measuring Exhaust Manifold Mounting Face For Warpage

   Courtesy of GENERAL MOTORS CORP.