284 Diesel Technology Copyright Goodheart-Willcox Co., Inc. This insulation aids in reducing heat radiation. Slip joints, sometimes referred to as expansion joints, are generally provided between the manifold sections and the turbo- charger or other outlet connections on most marine and mobile diesel engines. The exhaust manifold shown in Figure 13-8 serves as the passage for the gases from the cylinders to the exhaust inlet of the turbocharger. The turbine end of the turbo- charger is considered part of the exhaust system because it forms a part of the passageway for the escape of gases to the exhaust outlet. A similar arrangement is used on other turbocharged diesel engines. Exhaust Manifold Service When servicing an exhaust manifold, check it care- fully for cracks, burnout, and damaged threads. Be sure the inner passages are free of carbon buildup. Remove any metal chips or loose carbon from inside the manifold. If excessive carbon buildup exists, use a carbon solvent or carefully scrape the area clean. In severe cases, a combina- tion of solvent and scraping must be used. It is not advisable to remove a hot manifold from an engine, as this can promote warpage. Check for a warped manifold by placing a straightedge across the exhaust ports, Figure 13-9. The maximum allowable clearance between the manifold and the straightedge is usually about .004″ (.101 mm). Check the engine service manual for the exact clearance. If warpage is severe enough to prevent a good seal, the manifold must be machined or replaced. Exhaust Manifold Gasket An exhaust manifold gasket is used to prevent leakage between the mating surfaces of the engine and the mani- fold. While some engines are designed for no gasket, a gasket may eventually be required to compensate for warpage. Always clean the mating surfaces before installing a new manifold gasket, Figure 13-10. Use proper bolts or studs and torque them in the sequence recommended by the manufacturer. After the initial warm-up and cool-down, it may be necessary to retorque the bolts. Figure 13-7. Heat reduction is important in small marine engine applications. (Viking Yachts Inc.) Figure 13-8. The exhaust manifold serves as passageway for the gases traveling from the combustion spaces to the exhaust inlet of the turbocharger. Figure 13-9. A straightedge should be used when checking exhaust ports for warpage. (Mack Trucks, Inc.) Figure 13-10. After cleaning the mating surface, install the gasket. (Mack Trucks, Inc.)