Buick 12587310 Engine Exhaust Manifold Assembly

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Disconnect the cable from the negative terminal of the battery, then raise the vehicle and support it securely on jackstands. While working under the vehicle, apply penetrating oil to the exhaust pipe-to-manifold studs and nuts, allowing it to soak in before removing the nuts that retain the exhaust pipe to the manifold. Unplug the oxygen sensor electrical connector, remove the heat shield nuts, and take off the heat shield. Next, remove the exhaust manifold bolts to detach the manifold from the cylinder head, followed by removing the exhaust manifold gasket and cleaning the mating surfaces on both the cylinder head and manifold. Check the manifold for cracks and ensure the bolt threads are clean and undamaged, using a gasket scraper to eliminate all carbon deposits. Verify the manifold for warpage with a straightedge and feeler gauges; if it exceeds the limit, resurface it or replace it. Install a new gasket, then place the manifold on the cylinder head, applying heat-resistant thread locking compound to the bolt threads and starting the bolts by hand. Tighten the bolts in three passes, beginning from the center and moving to the ends, to the specified torque. Complete the remaining installation steps in reverse order, then start the engine and check for exhaust leaks.

For the left side manifold, disconnect the electrical connector from the Engine Coolant Temperature sensor, then remove the mounting bolts and separate the exhaust manifold from the cylinder head, also removing the heat shields.