GM 12557767 Engine Exhaust Manifold Assembly

Before critically removing the front exhaust manifold one has to disconnect the cable of the negative terminal from the battery. Lift the car and snugly put jackstands under the car then, Pop the lower splash pan if it is located below the front of the engine compartment, remove the engine cooling fans, the radiator. Before any procedure for the 1999 models, disconnect the air filter housing, left and right torque struts and the front engine mount nuts while there is a support from the floor jacks of the engine/transaxle subframe. The front engine mount brace has to be removed by lifting the engine/transaxle assembly carefully. Soak the exhaust manifold and exhaust flange bolts with penetrating oil and let it to set in, than unscrew the exhaust Y-pipe and separate it from the catalytic converter as well as remove the front oxygen sensor. Take off the rear alternator bracket, and exhaust flange nuts from the exhaust manifold, the exhaust crossover pipe also needs to be unbolted from the exhaust manifold from the cylinder head. For 2000 and later models, also remove the front oxygen sensor and the EGR pipe from the coolant crossover housing and exhaust crossover pipe, and note that the EGR pipe has a crush seal which must be replaced. If equipped, disconnect the left side coolant heater assembly, the oil dipstick tube, then spray the penetrating oil on the front exhaust manifold and un bolt it. Trim the rear exhaust manifold and unplug the connector for the rear oxygen sensor; lift the vehicle and safely support it on jack stands. For 1999 models remove exhaust Y-pipe from the catalytic converter, and suspension position sensor; also remove intermediate shaft of power steering gear and rear transaxle mount. Place the front part of the subframe on blocks, and set up the rear part of the engine/transaxle assembly subframe on a floor jack then unscrew the four subframe bolts to allow the lowering of the unit to reveal the rear exhaust manifold. Place the assembly on a jackstand, disconnect the exhaust Y-pipe from the exhaust manifold and then loosen the bolts joining the exhaust manifold to the cylinder head. Again for the 2000 and later models, you need to also take out the exhaust crossover pipe and the right side coolant heater assembly if there is and then remove the exhaust manifolds by unbolting them from the cylinder head. During installation, the manifolds and the fasteners must be checked for cracks and damages; the surface of the manifolds has to be scraped clean of old gasket material and carbon deposits; the new gaskets should be fitted over the cylinder head studs; and the manifolds properly installed, the mounting nuts to be tightened starting from the inside out to the recommended torque. Replace and bolt in the front engine mount and bracket, the radiator, the engine cooling fans, and fill the cooling system, start the engine and inspect for exhaust leaks. The following is the process of assembling the car; bolt the exhaust Y-pipe to the rear exhaust manifold, the intermediate shaft to the steering gear, others would be the reverse order of how they were removed but replace the gaskets when joining the exhaust pipes, fill the cooling system, start the car and check exhaust manifold gasket.

Before critically removing the front exhaust manifold one has to disconnect the cable of the negative terminal from the battery. Lift the car and snugly put jackstands under the car then, Pop the lower splash pan if it is located below the front of the engine compartment, remove the engine cooling fans, the radiator. Before any procedure for the 1999 models, disconnect the air filter housing, left and right torque struts and the front engine mount nuts while there is a support from the floor jacks of the engine/transaxle subframe. The front engine mount brace has to be removed by lifting the engine/transaxle assembly carefully. Soak the exhaust manifold and exhaust flange bolts with penetrating oil and let it to set in, than unscrew the exhaust Y-pipe and separate it from the catalytic converter as well as remove the front oxygen sensor. Take off the rear alternator bracket, and exhaust flange nuts from the exhaust manifold, the exhaust crossover pipe also needs to be unbolted from the exhaust manifold from the cylinder head. For 2000 and later models, also remove the front oxygen sensor and the EGR pipe from the coolant crossover housing and exhaust crossover pipe, and note that the EGR pipe has a crush seal which must be replaced. If equipped, disconnect the left side coolant heater assembly, the oil dipstick tube, then spray the penetrating oil on the front exhaust manifold and un bolt it. Trim the rear exhaust manifold and unplug the connector for the rear oxygen sensor; lift the vehicle and safely support it on jack stands. For 1999 models remove exhaust Y-pipe from the catalytic converter, and suspension position sensor; also remove intermediate shaft of power steering gear and rear transaxle mount. Place the front part of the subframe on blocks, and set up the rear part of the engine/transaxle assembly subframe on a floor jack then unscrew the four subframe bolts to allow the lowering of the unit to reveal the rear exhaust manifold. Place the assembly on a jackstand, disconnect the exhaust Y-pipe from the exhaust manifold and then loosen the bolts joining the exhaust manifold to the cylinder head. Again for the 2000 and later models, you need to also take out the exhaust crossover pipe and the right side coolant heater assembly if there is and then remove the exhaust manifolds by unbolting them from the cylinder head. During installation, the manifolds and the fasteners must be checked for cracks and damages; the surface of the manifolds has to be scraped clean of old gasket material and carbon deposits; the new gaskets should be fitted over the cylinder head studs; and the manifolds properly installed, the mounting nuts to be tightened starting from the inside out to the recommended torque. Replace and bolt in the front engine mount and bracket, the radiator, the engine cooling fans, and fill the cooling system, start the engine and inspect for exhaust leaks. The following is the process of assembling the car; bolt the exhaust Y-pipe to the rear exhaust manifold, the intermediate shaft to the steering gear, others would be the reverse order of how they were removed but replace the gaskets when joining the exhaust pipes, fill the cooling system, start the car and check exhaust manifold gasket.