CYLINDER GP-HYDRAULIC 3679481 - Caterpillar

3400 Family Of EnginesSUPPLEMENT: 12/24/90Service Magazine; February 12, 1990; Page 14; "New Exhaust Manifold Studs Available."Disregard this article and see the article "Update Information For Exhaust Manifolds" in this issue.--------------- END SUPPLEMENT ---------------Reference: Service Magazine: March 28, 1988; Page 2; "New Exhaust Manifold Sections And Gaskets Used In Exhaust Manifold Groups." Services Magazine; December 12, 1988, Page 5; "Maintenance Procedure Extends Service Life Of Exhaust Manifold Studs" for 3400 Family Of Engines.The exhaust manifold studs may fail due to exhaust manifold movement. The studs are more likely to fail in extreme conditions such as high altitude and high exhaust manifold temperatures.
The new 9X2840 Stud can be used to replace the former 6V5699 Stud. The 8M2296 Stainless Steel Nut should be used with the new stud.
The following procedure can be used to retain the exhaust manifolds and at the same time allow for manifold movement to help prevent stud failure.
1. Remove the manifolds from the engine. DO NOT separate the exhaust manifold sections as outlined in the above reference articles.2. Replace any broken studs with the new 9X2840 Stud.3. Use a suitable method (such as an end mill) to elongate the existing holes as shown in Illustration 1, 2 and 3. The dimensions for the slots are shown in Illustration 4. If the machine 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 exhaust manifolds using new 9Y4582 Manifold Gaskets.