The Nissan Xterra has one exhaust manifold with a four-cylinder engine or two with a V6 engine.The manifold connects the engine and cylinder heads to the exhaust pipe. If an exhaust manifold is cracked or leaking, you need to replace it to prevent harmful exhaust from seeping into the truck.
Disconnect the Xterra's negative battery cable.
Raise the front end of the truck and support it on jack stands. Block the rear wheels with wheel chocks or large blocks.
Remove the engine splash shields if the Xterra is equipped with them by removing their bolts with a wrench.
Remove the three nuts connecting the exhaust pipe from the manifold to disconnect the two components.
Unscrew and remove the air intake duct with the air cleaner's top half from the throttle body, then unscrew and remove the bracket for the oil dipstick from the manifold. This is required only for the left manifold on a V6 engine.
Disconnect the lower heat shield from the exhaust manifold, which is in the engine compartment. It has four nuts. Disconnect the oxygen sensor's electrical connector, then remove the upper heat shield by removing its seven nuts.
Unbolt and disconnect the EGR pipe from the manifold.
Remove the mounting nuts connecting the manifold to the cylinder head; remove the ones on the outer edges first and work your way to the middle of the manifold. Detach and remove the manifold with its gaskets.
Scrape away all traces of gasket material and carbon deposits from the cylinder head mating surface, and make sure no such material is on the replacement exhaust manifold. Place new gaskets on the studs on the cylinder heads.
Install the new exhaust manifold in place on the cylinder heads and thread the mounting nuts onto the studs by hand. Tighten the nuts with the wrench, starting with the middle nuts and working your way outward.
Reconnect the other parts--the EGR pipe, the upper and lower heat shields for the manifold, the oxygen sensor's electrical connector, the exhaust pipe and the splash shields. Apply an anti-seize compound to the exhaust pipe's studs and the EGR pipe's nut when connecting these component.
Lower the truck off the jack stands and reconnect the battery cable.
