Buick 12670220 Exhaust Manifold Assembly

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To remove the components, start by taking off the air cleaner housing and the drivebelt, then raise the vehicle securely on jackstands. Once the engine has cooled, soak the manifold retaining nuts with penetrating oil to loosen any rust. Disconnect the air inlet hoses from the throttle body and remove the intake air resonator. Detach the retainers connecting the engine wiring harness to the A/C pressure hose and accessory mounting bracket, followed by removing the nuts attaching the power steering hoses to the A/C compressor stud. Take out the power steering pump from the accessory mounting bracket and tie it out of the way. Disconnect the vacuum brake booster hose and wiring harness from the power steering reservoir, then remove the reservoir mounting fasteners and set it aside. Disconnect the electrical connector from the A/C compressor, remove the mounting bolts, and tie the compressor out of the way without allowing it to hang unsupported. Remove the accessory mounting bracket from the engine and unplug the heated oxygen sensor electrical connector. Take off the catalytic converter-to-exhaust manifold mounting fasteners and lower the converter, then remove the exhaust manifold retaining nuts, the exhaust manifold, and the old manifold gasket, noting that removing the oxygen sensor may facilitate access. If any studs are damaged, use a stud removal tool or two nuts tightened against each other to extract them. On the right side, repeat the process of removing the drivebelt and tensioner, disconnecting the harness clips from the ECM bracket, and removing the after run coolant pump-to-ECM mounting bracket fasteners. Remove the starter motor, unplug the heated oxygen sensor electrical connector, and lower the catalytic converter from the manifold. Again, remove the exhaust manifold retaining nuts, the exhaust manifold, and the old gasket, checking for the need to remove the oxygen sensor for easier access. Inspect the exhaust manifolds for cracks or damage, replacing any that are compromised. Use a scraper to remove gasket material from mating surfaces, being cautious not to scratch or gouge them, and inspect for wear and cracks. Check the exhaust manifold mating surface for warpage using a straightedge and feeler gauge, replacing or resurfacing any components that exceed limits. If any studs are damaged, install new exhaust studs in the cylinder head, then install the manifold with a new gasket and self-locking nuts, coating the threads with anti-seize compound. Tighten the nuts in stages from the center out to the specified torque, and complete the installation in reverse order of removal, running the engine afterward to check for exhaust leaks.

Tighten the bolts from the center to the ends using a torque wrench in two steps.

Place the manifold on the cylinder head and install the mounting bolts finger tight.

For installation, clean the mating surfaces on the cylinder head, manifold, and exhaust pipe with a scraper and brake system cleaner, ensuring they are flat and undamaged. Install a new gasket on the cylinder head, place the manifold, and tighten new exhaust manifold bolts evenly from the center outwards to the specified torque. Note that the new bolts have adhesive coating and should be tightened within five minutes. The installation process is the reverse of removal, followed by reconnecting the battery and checking for exhaust leaks after running the engine.