GM 14091886 Manifold

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Disconnect the negative battery cable from the battery. Caution: On models equipped with the Delco Loc II audio system, make sure the lockout feature is turned off before performing any procedure that requires disconnecting the battery. Unplug the oxygen sensor. Remove the manifold heat shields. Raise the vehicle and securely support it on jackstands, then remove the exhaust pipe-to-manifold nuts. The nuts are usually rusted in place, so penetrating oil should be applied to the stud threads before attempting to remove them. Loosen them a little at a time, working from side to side to prevent the flange from jamming. Remove the exhaust manifold brace. Separate the exhaust pipe flange from the manifold studs, then pull the pipe down slightly to break the seal at the manifold joint. Loosen the exhaust manifold mounting nuts 1/4-turn at a time, working from the inside out, until they can be removed by hand. Separate the manifold from the head and remove it. The manifold and cylinder head mating surfaces must be clean when the manifold is reinstalled. Use a gasket scraper to remove all traces of old gasket material and carbon deposits. Using a new gasket, install the manifold and hand tighten the fasteners. Working from the center out following the recommended sequence, tighten the bolts/nuts. The remaining installation steps are the reverse of removal.

Disconnect the negative cable from the battery. Caution: On models equipped with the Delco Loc II audio system, make sure the lockout feature is turned off before performing any procedure that requires disconnecting the battery. Unplug the oxygen sensor lead. Remove the drive belt and the alternator. Raise the front of the vehicle, support it securely on jackstands, and apply the parking brake. Block the rear wheels to prevent the vehicle from rolling off the jackstands. Unbolt the exhaust pipe from the manifold. Lower the vehicle. Remove the eight exhaust manifold-to-cylinder head nuts/bolts, pull the manifold off the engine, and lift it out of the exhaust pipe flange. Remove and discard the gasket. Scrape off all traces of gasket material from the exhaust manifold and cylinder head mating surfaces. Clean all bolt and stud threads before installation. Use a wire brush on the manifold mounting studs, and a tap works well for cleaning the cylinder head bolt holes. If installing a new manifold, transfer the oxygen sensor from the old manifold to the new one. Installation is the reverse of removal. Be sure to use a new gasket and tighten the nuts/bolts. Work in a spiral pattern from the center out.

For the front manifold removal, start by disconnecting the negative battery cable and removing the air cleaner assembly, inlet hose, and mass air flow sensor. Allow the engine to cool, drain the coolant, and disconnect the coolant bypass tube if needed. Remove the cooling fan assembly and the oil dipstick tube mounting bolt. On early models with tubular steel manifolds, disconnect the front manifold extension pipe near the rear manifold. On later models with cast iron manifolds, unbolt the crossover pipe from the front manifold. Remove the manifold heat shield and the mounting bolts, then detach the manifold from the cylinder head. Clean the mating surfaces, inspect the manifold for distortion and cracks, and if necessary, resurface it at an automotive machine shop. Install the manifold with a new gasket and tighten the mounting bolts gradually, starting from the middle and working outward. Reassemble the remaining components in reverse order and check for exhaust leaks. For the rear manifold removal, begin by disconnecting the negative battery cable and allowing the engine to cool. Disconnect the EGR tube from the exhaust manifold and remove the throttle and TV cables and brackets if necessary. Remove the heat shield and unbolt the crossover pipe (or front manifold extension pipe) from the rear manifold. Disconnect the oxygen sensor wire and, if replacing the manifold, transfer the sensor to the new one. Set the parking brake, block the rear wheels, and raise the front of the vehicle on jackstands. Working beneath the vehicle, remove the two exhaust pipe-to-manifold bolts, applying penetrating oil if needed. Unbolt and remove the exhaust manifold. Clean the mating surfaces, check for warpage and cracks, and resurface at an automotive machine shop if necessary. Place the manifold with a new gasket and install the bolts finger-tight, gradually tightening from the middle outwards. Reassemble the remaining components in reverse order and check for exhaust leaks after starting the engine.