GM 90570541 Engine Exhaust Manifold Assembly

Disconnect the cable from the negative battery terminal. Raise the vehicle and support it securely on jackstands. Remove the splash shield from below the engine compartment. Working under the vehicle, apply penetrating oil to the exhaust pipe-to-manifold studs and nuts. Drain the coolant. Remove the oxygen sensor from the exhaust manifold. Install an engine support fixture and remove the transaxle mount through-bolt. Raise the engine slightly to access the coolant extension housing. Remove the oil dipstick and dipstick tube. Remove the coolant extension housing. Remove the power steering pipe bracket. Remove the front exhaust pipe assembly. Remove the oil filter housing assembly. Remove the mounting nuts from the exhaust manifold, then detach the manifold from the cylinder head. Disconnect the EGR pipe from the exhaust manifold. Remove the oxygen sensor from the exhaust manifold. Remove the rear exhaust pipe assembly from the vehicle. Remove the mounting nuts from the exhaust manifold, then detach the manifold from the cylinder head. Check the exhaust manifolds for cracks. Make sure the bolt threads are clean and undamaged. The exhaust manifold and cylinder head mating surfaces must be clean before the exhaust manifolds are reinstalled- use a gasket scraper to remove all carbon deposits. Position a new gasket in place and slip the exhaust manifold over the studs on the cylinder head. Install the mounting nuts. When tightening the mounting nuts, work from the center outwards, alternating between top and bottom rows. Tighten the bolts to the specific torque. The remaining installation steps are the reverse of removal. When reconnecting the EGR tube to the exhaust manifold, use a slight amount of anti-seize compound on the threads. If the front exhaust manifold was removed, refill the cooling system. Reconnect the battery. Start the engine and check for leaks.

Check the mating surface for flatness and damage; if warped or damaged, machining or replacement may be necessary.

Penetrating oil should be applied to the exhaust pipe-to-manifold studs and nuts.

Install the new gasket to the cylinder head studs and place the manifold on the cylinder head. Tighten the nuts evenly, working from the center outwards, to the specific torque.