For 1990-2009 cars

Note: 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 affect on-board diagnostics (OBD) II system performance.

1. Clean the exhaust manifold in solvent.

Warning: Refer to Safety Glasses Warning in the Preface section.

2. Dry the exhaust manifold with compressed air.
3. Internal heat cracks are allowed. Do not replace the exhaust manifold for this condition.
4. Inspect the heat shield for damage.
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 (0.0100 in) may cause an exhaust leak and may affect OBD II system performance. Exhaust manifolds not within specifications must be replaced.