OEM GMC Sierra 3500 Classic Exhaust Manifold

GMC Sierra 3500 Classic Exhaust Manifold Parts and Q&A

• Exhaust Manifold, Driver Side
  12616285
  Q: How to replace the left side exhaust manifold on 4.8L, 5.3L, 6.0L, and 6.2L engines on GMC Sierra 3500 Classic?

  A:

  You need to start the left side Exhaust Manifold replacement on 4.8l, 5.3l, 6.0l, and 6.2l engine vehicles by inserting the Steering Column anti-rotation pin (J 42640) through the Steering Column lower access hole. Attack the replacement by first removing the wheelhouse liner from the left side while elevating and securing the vehicle. Catalytic Converter to Exhaust Manifold nuts must be removed so you can lower the vehicle partway through the wheel opening. This procedure includes the 1500 series and similar 2500 series exhaust manifolds. To disconnect Spark Plug Wires from their components twist the wire boot 1.5 times and only pull the boot portion. Start by marking the connection position of upper intermediate Steering Shaft relative to the Steering Column before unbolting and unthreading the coupling components and from the Steering Shaft. This action separates the Steering Shaft from the Steering Column. The mechanic will remove all the Exhaust Manifold bolts and extract the Exhaust Manifold while discarding both the gasket and seal. The removal of Exhaust Manifold heat shield requires disconnecting heat shield bolts as well as the removal of the heat shield itself. Secure the Exhaust Manifold heat shield by installing its bolts while tightening them to 9 n.m (80 lb in). Disassemble the Exhaust Manifold bolts before applying threadlock gm p/n 12345493 (Canadian P/N 10953488) to the threads with a 5 mm (0.2 in) wide band. Apply the new Catalytic Converter seal before installing the new Exhaust Manifold Gasket and Exhaust Manifold to the cylinder head while ensuring correct mounting to the Catalytic Converter. Begin installing Exhaust Manifold bolts by starting from the middle ones then alternately between sides before achieving a final torque of 20 n.m (15 lb ft) with the same bolt order. The flat punch enables bending of the gasket tab at the Exhaust Manifold's rear part around the cylinder head surface. Secure the upper intermediate Steering Shaft to the Steering Column by aligning its marks first before applying the Steering Shaft coupling bolt and nut and tightening it to 50 n.m (37 lb ft) torque. After wiring the spark plugs and coils with Spark Plug cables, check the wires to ensure correct installation. Raise the vehicle fully and install the Catalytic Converter to Exhaust Manifold nuts before tightening them to 50 n.m (37 lb ft). Lower the vehicle partially while reinstalling the left wheelhouse liner until you retrieve the Steering Column anti-rotation pin (J 42640) from the lower access hole of the Steering Column.
• Exhaust Manifold
  12677665
  Q: How to replace the right side exhaust manifold (4.8L, 5.3L, 6.0L, and 6.2L) on GMC Sierra 3500 Classic?

  A:

  The right side Exhaust Manifold replacement process (4.8L, 5.3L, 6.0L, and 6.2L) begins with heated Oxygen Sensor (HO2S) removal followed by vehicle suspension and subsequent removal of the Catalytic Converter to Exhaust Manifold nuts and right wheelhouse liner before disconnecting Spark Plug Wires and Ignition Coils and extracting the engine block's oil level indicator tube bolt and tube. Begin the procedure by taking off the Catalytic Converter to Exhaust Manifold nuts along with removing the right wheelhouse liner and disconnecting Spark Plug Wires from spark plugs through boot twisting by half turn and boot pulling. After removing the ignition coils follow by taking out both the oil level indicator tube bolt (419) along with the tube (420) from the engine block. Discard the Exhaust Manifold Gasket and seal as you proceed to take out the Exhaust Manifold bolts and Exhaust Manifold itself. When replacing the Exhaust Manifold users must remove all Exhaust Manifold heat shield bolts while simultaneously disconnecting its shield from the exhaust pipe. Install the Exhaust Manifold heat shield by positioning it then fastening its bolts to 9 n.m (80 lb in). Prepare each Exhaust Manifold bolt thread and apply gm p/n 12345493 threadlock (Canadian P/N 10953488) as a 5 mm (0.2 in) thick strip on the threads. Position the new Catalytic Converter seal alongside the Exhaust Manifold Gasket and Exhaust Manifold onto the cylinder head while verifying appropriate seating of the Catalytic Converter seal. Begin by installing the Exhaust Manifold bolts with an initial torque of 15 n.m (11 lb ft) that progresses from the center toward the outside bolts by alternating between sides before conducting a final torque of 20 n.m (15 lb ft) applying the same alternating sequence. A flat punch should be used to bend the gasket tab at the cylinder head edge while inspecting the o-ring seal (421) for damage before either replacement or lubrication of the o-ring with clean engine oil. Install the oil level indicator tube (420) while tightening bolt (419) to 25 n.m (18 lb ft). Seamlessly reconnect the Spark Plug Wires with the spark plugs and ignition coils through a boot seating check by applying side pressure. Complete the procedure by putting back the right wheelhouse liner while the vehicle is fully raised then support it before you install the Catalytic Converter and Exhaust Manifold nuts which need tightening to 50 n.m (37 lb ft). Finish by lowering the vehicle partially so you can work through the wheel opening and place the ho2s.