Put the cable back on to the negative battery terminal, lock the back wheels, and pull up the brake. Start by lifting the front of the car and putting jackstands below it, then take off the lower splash shield under the engine that many cars have. While the car is off, put penetrating oil on the fasteners of the exhaust pieces and give it time to affect the metal. Unhook the Y-pipe on the exhaust from the vehicle, and unscrew the oxygen sensor connectors. In G35 models, disconnecting the steering joint for the left-side manifold requires setting aside the lower steering shaft before proceeding to the work. Take off the exhaust heat shield, then pull out the catalytic converters by carefully loosening the bolts that fasten the upper heat shield to the exhaust manifolds, then soaking and unbolting the bands connecting the front end of the converters. For G35 models, you have to first take out coolant and detach the tube running alongside and through the front and both sides of the engine to take off the left exhaust manifold. Take out bolted nuts/connecting pieces. Then lift the manifold off with the gasket attached. Brush any remains of gasket and carbon deposit off the parts where the cylinder head joins the manifold. Put the new exhaust manifold gaskets on top of the studs on your cylinder head, and then make sure they go on with the arrow facing upward after placing them correctly. Put the manifold in place, and start screwing the fastening nuts and bolts by hand. Begin from the center and work outwards, tighten all nuts/bolts in two steps to reach the correct torque level. After putting back the parts that came off, start the engine to find and fix any exhaust leak problems.
