Usage:
3400 Family of Engines
- SUPPLEMENT: 12/24/90
Service Magazine; December 12, 1988; Page 5; "Maintenance Procedure Extends Service Life Of Exhaust manifold Studs." Disregard this article and see the article "Update Information For Exhaust Manifolds" in this issue.
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Reference: Service Magazine; March 28, 1988; Page 2; "New Exhaust Manifold Sections And Gaskets Used In Exhaust Manifold Groups."
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 new 9Y4582 Exhaust Manifold Gasket announced in the reference article combined with the use of higher grade 6V5699 Studs and 8M2296 Nuts for 3408 and 3412 Engines have improved torque retention in these applications.
Thorough preparation of the exhaust manifolds before assembly, as described in the following procedure, and use of the new gaskets and hardware can prevent stud breakage.
Procedure For Repairing Exhaust Manifolds
1. 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 used on 3406 Engines can be replaced with a higher strength stainless steel 6V5699 Stud. (Use the 8M2296 Nut, if the 6V5699 Stud is replaced. The 2N2766 Locknut should be used with the 4S6137 Stud.)
NOTE: Make sure that heat treat scale on the threads of the 6V5699 Stud does not cause artificially low nut torques at assembly by creating thread interference (galling). The use of 8M2296 Nut with this stud will reduce the thread interference.
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.
NOTE: After the cleaning process, the stud clearance holes can be reamed to 11.5 mm (.45") maximum diameter to allow for easier assembly.
3. Make sure the male end of the manifold is clean, dry and free from grease and oil. Apply a thin, uniform coat of 2P2333 Manifold Sealer to the male end of the manifold sections.
4. Apply engine oil only to the female end of the manifold sections. This will keep the sealer from sticking to the female portion of the joint.
5. 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.
6. Assemble the manifold sections. Allow the sealer to cure thoroughly (over night if possible) before starting the engine.
The sealant should:
...prevent oxidation on the joint and maintain the expansion capability of the joint,
...minimize potential exhaust gas leaks from the newly cleaned joints,
...prevent water entry into the exhaust manifolds of 3406B Engines when the engines are washed.
7. Put 5P3931 Anti-seize Compound on the stud threads, install the correct nuts or locknuts as explained in Step 1 and tighten to 52 ± 7 N·m (38 ± 5 lb ft) using the sequence shown in the Service Manual.