GM 12629337 Exhaust Manifold

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To remove the exhaust manifold, first disconnect the cable from the negative terminal of the battery, then raise the vehicle and support it securely on jackstands. Apply penetrating oil to the exhaust pipe-to-manifold studs and nuts, as they are often rusty. Remove the inner fender splash shield and disconnect the exhaust pipe/catalytic converter pipe from the exhaust manifold. Remove the spark plug wires by twisting the boots to loosen them and pulling only on the boots. On the left side, mark the alignment of the upper section of the steering intermediate shaft to the lower part of the steering column before removing the fasteners and separating the shafts, ensuring not to move the wheels or steering wheel to avoid damaging the airbag system clock spring. For 6.0L models, install a special tool into the steering column lower access hole to prevent rotation. On the right side, remove the oil dipstick tube if applicable. If a new manifold is to be installed, remove the heat shield and the manifold mounting bolts, then lift off the exhaust manifold and its gasket. Before installation, check the manifold for cracks and ensure the bolt threads are clean and undamaged, using a gasket scraper to clean the mating surfaces without aggressive scraping. Install the heat shields, bolts, and gaskets onto the manifold, ensuring the retaining tabs hold the assembly together. Apply a 1/4-inch wide band of medium-strength thread locking compound starting at the fourth thread, avoiding the first three threads. Place the manifold on the cylinder head and install the mounting bolts finger tight, then tighten them from the center to the ends in two steps to the specified torque. If necessary, bend the exposed end of the exhaust manifold gasket back against the cylinder head. Complete the installation in reverse order of removal and start the engine to check for exhaust leaks.

The nuts should be removed by accessing them from underneath the vehicle or through the fenderwell opening if necessary.