Exhaust Manifold Torque Specsby John Walker
The exhaust manifold is a large metal block bolted to the side of the engine, and it connects the exhaust pipe to the main engine block. To locate the exhaust manifold, trace your exhaust pipe to where the round pipe bolts to a two-bolt connection near the engine. The solid structure to which the pipe is bolted is the exhaust manifold. Installing a manifold requires careful torquing of the bolts.
Amount of Torque
Every vehicle has different levels of torque necessary to properly tighten its bolts. The standard is to use 20 to 30 foot-pounds of torque. Older engines often fall on the lighter side of the equation, so use 15 to 20 foot-pounds of torque if your engine is 15 years old or older. Some manifolds house different sensors and plugs, such as a check valve or exhaust plug. The different elements require less torque than the bolts on the manifold. Use between 10 and 17 foot-pounds of torque for those elements. The precise torque for your vehicle can be identified in the vehicle-specific repair manual, available from an auto parts retailer.
Clean off any used gasket material, and install a new gasket when you take the manifold off the vehicle. Torquing the bolts properly requires following a set pattern. The pattern helps the new gasket sit correctly against the engine blocking leaks. Hand-tighten all bolts initially. Torque the bolts in sequence to half the amount of torque necessary. Start with the middle bolts, and work your way toward the edges one bolt at a time. Repeat the process using the full torque necessary.
In most vehicles, the manifold is covered by a heat shroud, which is a simple piece of formed aluminum. The metal acts as a heat damper to prevent excessive heat from bouncing around in the engine. You must remove the heat shroud before working on the manifold. When installing the shroud, use 10 to 12 foot-pounds of torque. You also should inspect the length of the exhaust pipe for damage. When servicing the exhaust, you should disconnect each bolted connection, clean the surface of the connection and install new gaskets at each joint. You can unbolt each connection and separate the joint by several inches without removing the unit from the vehicle.
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