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.

Clean the exhaust manifold (600) and heat shield (603) in solvent.
Dry the exhaust manifold with compressed air.
Inspect the exhaust manifold-to-cylinder head gasket surface for excessive scratches or gouging.

Fig 1: View Of Manifold, Heat Shield & Bolts
Courtesy of GENERAL MOTORS CORP.
Inspect for a loose or damaged heat shield (603).
Inspect the exhaust pipe studs for damaged threads.
Use a straight edge and a feeler gage and measure the exhaust manifold cylinder head deck for warpage.

Fig 2: Measuring Exhaust Manifold To Cylinder Head Surface For Warpage
Courtesy of GENERAL MOTORS CORP.

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 effect OBD II system performance. Exhaust manifolds not within specifications must be replaced.