CONNECTOR 9X8408 - Caterpillar

3400 Family Of EnginesThis article supersedes all earlier articles on exhaust manifolds for these engines.
Oxidation and scale can accumulate in the expansion joints of the exhaust manifold sections. This build-up prevents the relative movement of each manifold section during engine operation. As the manifold assembly expands, it exerts pressure on the studs that can lead to stud breakage. The studs are more likely to fail in extreme conditions such as high altitude and high exhaust manifold temperatures.
The new 9Y4582 Exhaust Manifold Gasket combined with the use of higher alloy 9X2840 Studs (formerly 6V5699 Studs) and 8M2296 Stainless Steel Nuts have improved torque retention and reduced stud breakage on service repair. Also, one of the two following procedures will help eliminate stud breakage.
Procedure For Repairing Exhaust Manifold As An Assembly
1. Remove the manifolds from the engine. DO NOT separate the exhaust manifold sections. Tack weld the manifold sections at the joints to prevent thermal ratcheting which can occur from joint "slippage" at high temperatures.2. Remove any broken studs. Because of the extreme hardness of the stud, weld a nut onto the broken stud to provide an effective way of removing the stud. Replace any broken stud with the new 9X2840 Stud and 8M2296 Nut. DO NOT mix production 4S6137 Studs and 2N2766 Locknuts with the new, higher alloy studs and stainless steel nuts.3. Use a suitable method (such as an end mill) to elongate the existing holes as shown in Illustrations 1, 2 and 3. The dimensions for the slots are shown in Illustration 4. If the engine is being repaired in the field and an end mill is not available, the same holes shown in Illustrations 1, 2 and 3 can be enlarged to 12.7 mm (.50") using a reamer.
Illustration 1. Exhaust manifold for 3406 Engine.
Illustration 2. Exhaust manifold for 3408 Engine.
Illustration 3. Exhaust manifold for 3412 Engine.
Illustration 4. Dimensions for slots.4. Install the new 9Y4582 Manifold Gaskets on the studs between the manifolds and the cylinder head. This gasket is thicker and denser than the former gasket and will improve nut torque retention.5. Put 5P3931 Anti-Seize Compound on the stud threads. Install the correct nuts or locknuts as explained in Step 2 and tighten to 52 7 N m (38 5 lb ft) using the sequence shown in the Service Manual.Procedure For Repairing Exhaust Manifolds With Sections Separated
1. Remove the manifold from the engine. Remove any broken studs. Because of the extreme hardness of the stud, weld a nut onto the broken stud to provide an effective way of removing the stud. The 4S6137 Stud can be replaced with a higher strength stainless steel 9X2840 Stud. (Use the 8M2296 Nut, with the 9X2840 Stud. The 2N2766 Locknut should be used with the 4S6137 Stud.)2. Disassemble the exhaust manifold sections. Clean the joints thoroughly with a wire brush to remove all existing carbon, oxidation and scale. Finish removing any remaining residue with 80 grit abrasive cloth. After the cleaning process, the stud clearance holes can be