1993/07/01 Caterpillar

3406B/C (3ZJ, 4CK, 5KJ) Truck Engines

Description of Change: New exhaust manifold end sections and center sections are used in the exhaust manifold groups on 3406 engines with dry type exhaust manifolds. The part numbers of the exhaust manifold groups did not change. The new manifold sections incorporate the following improvements:

* A 10.5 mm (.41 in.) diameter slotted hole 15.0 mm (.59 in.) wide alternating from the top to the bottom at each mounting flange for increase stud clearance with thermal expansion and for improved horizontal alignment of the slip joints.

* A 15.0 mm (.59 in.) diameter hole at each flange adjacent to the slotted holes for increased stud clearance.

NOTE: Only one slotted hole at each flange is needed for alignment of the slip joints.

* Milled flanges instead of spot faces to insure adequate clearance around the 2S3770 Spacers with the larger flange holes and slots.

* Thinner wall thickness at female slip joints to reduce expansion stresses against male slip joints.

* Grooves removed from the male slip joints to improve exhaust gas sealing.

* Increased socket clearance around the studs and nuts to ease installation.

* Long stud and spacer at the lower flange of number 3 cylinder to better retain nut torque by increasing stud stretch.

NOTE: The long stud and spacer are the same 4S6137 Stud and 2S3770 Spacer used at the other mounting holes. This position formally used a short 6L8562 Stud and no spacer.

Adaptable To: The new and former exhaust manifold end and center sections are identified in Charts A and B. The exhaust manifold group part numbers did not change. The new manifold end and center sections are in effect with 3406B/C Truck Engines 3ZJ29729, 5KJ7904, and 4CK7039.

A 9U7224 Manifold Installation Guide is available to align the manifold studs in the center of the slotted and oversize holes during installation of the exhaust manifold group. Since each flange has slotted and oversize holes, a 9U7224 Installation Guide is required for each manifold section. The installation guide is slid over a stud and into the upper 15.0 mm (.59 in.) oversize holes in each manifold section. The spacers, washers and nuts can then be installed on the other nine studs and loosely tightened to hold the manifold group in place. The installation guides can then be removed and the remainder of the spacers, washers and nuts installed.

NOTE: It is recommended that the 9U7224 Installation Guides be used at the upper oversize holes at locations 11, 7 and 9 as indicated on the Exhaust Manifold Nut Tightening Sequence Illustration that follows. If the guides can not be used at location 11 or 9 because of a clearance problem at the cab or temperature regulator housing, they can be installed at locations 12 and 10.

Exhaust Manifold Nut Tightening Sequence

A new nut tightening sequence is required with the new exhaust manifolds. Tighten the nuts, in the sequence shown, to a torque of 38 ± 5 N·m (28 ± 4 lb ft).

NOTE: This nut torque has been used in production since February 1992 and can be used with all 3400 Engine exhaust manifold groups. Use 5P3931 Anti-Seize Compound on the studs. New 2N2766 Lock Nuts should always be used. Do NOT use an impact wrench to run the nuts down, the threads will be galled. This can cause false torque readings when the nuts are tightened.

When assembling the manifold sections, make sure that the male end of the manifold end sections is clean, dry, and free of grease or oil. Apply a thin uniform coat of 2P2333 Manifold Sealer to the male end of the end sections. Apply a thin coat of engine oil to the female ends of the manifold center section. After installing the assembled exhaust manifold group on the engine, allow the manifold sealer to cure thoroughly (overnight if possible) before starting the engine.

If a previous end or center section is damaged beyond repair, the new manifold sections are interchangeable. When replacing a previous manifold section make sure to use the equivalent new part as indicated in the above charts.