0377321 JOHNSON CLAMP, Exh., relief boot

The information supplied in this service letter may not be valid after the termination date of this program. Do not perform the work outlined in this Service Letter after the termination date without first contacting your Caterpillar product analyst.
This Program can be administered either before or after a failure. In either case the decision whether to apply the Program is made by the dealer. When reporting the repair, use "PS8467" as the Part Number and "7755" as the Group Number. If administered before failure, use "56" as the Warranty Claim Description Code and use "T" as the SIMS Description Code. If administered after failure, use "96" as the Warranty Claim Description Code and use "Z" as the SIMS Description Code.
This Revised Service Letter replaces the October 4, 1995 (Revised September 1996) Service Letter. Changes have been made to the TERMINATION DATE.
Termination Date
August 31, 1997Problem
Coolant loss caused by combustion gas leakage and afterboil on quick speed reductions, exhaust valve failures, low idle oil pressure alarm sounding at low RPM, injector hold-down bolt breakage, and rocker arm failures may occur on certain 3126 Marine Engines.
Affected Product
Model & Identification Number
Group 1
3126 (8NM20-524)
Group 2
3126 (8NM20-895)
Group 3
3126 (8NM20-567)
Group 4
3126 (8NM20-611)
Group 5
3126 (8NM20-624)
Group 6
3126 (8NM20-1714)
Parts Needed
Group 1
1 - 1028392 Regulator-TemperatureGroup 2
1 - 3J7352 Connector 3 - 3J7354 Seal 4 - 1P4278 Clamp 1 - 5P4536 Elbow 1 - 5P6442 Hose (two pieces 14.2cm and 95cm) 4 - 4P5918 Clip 4 - 3S2093 Strap-Cable 1 - 4S4857 Tee 3 - 2V4869 Fitting 1 - 0520572 Tee14 - 1274836 Bolt-Hex Head PARTS NEEDED CONT.
Group 3
No parts are required for the Group 3 rework procedure.
Group 4
- 1154190 Rocker Arm Assembly (Quantity needed is determined after inspection)
Group 5
1 - 1221522 Switch Assembly-Pressure
Group 6
No parts are required for the Group 6 rework procedure.
Action Required
See the attached procedure.
Service Claim Allowances
Labor Hour Breakdown Parts Disposition
Handle the parts in accordance with your Warranty Bulletin on warranty parts handling.
MAKE EVERY EFFORT TO COMPLETE THIS PROGRAM AS SOON AS POSSIBLE.
Attach.(1-Rework Procedure)Rework Procedure
Group 1
8NM20-524
Replace the existing coolant temperature regulator with a new 1028392 Temperature Regulator.
Group 2
8NM20-558
1. Remove and replace the existing head bolts, one bolt at a time in standard torque sequence, with 14 new 1274836 Hex Head Bolts.2. Add MOLY LUBE to the bolt threads and washer face before installing.3. Torque each bolt to specification in standard torque sequence.4. (If accessible without removing the head) Drill and tap NPT 16.5mm from the top rear face and 29.5mm from the top right face of the cylinder head.5. Add the rear exhaust cylinder head vent to the expansion tank. 8NM559-753
1. Remove head bolts one bolt at a time in standard torque sequence.2. Clean threads.3. Apply MOLY LUBE to the bolt threads and washer face before installing.4. Torque each bolt to specification in standard torque sequence. 8NM20-895
1. (If accessible without removing the manifold) Drill and tap NPT at the top rear of the exhaust manifold. 2. Add the rear exhaust manifold vent to the expansion tank. If neither the cylinder head nor exhaust manifold has a vent, and neither is accessible to add the vent in the boat, then remove the exhaust manifold to drill and tap for venting, so that at least one or the other will be vented.
Group 3
8NM20-567
1. Set the injector timing height to 65.40 mm and stamp the information plate on the valve cover.2. Set the exhaust valve lash to .030 inch.Group 4
8NM20-611
1. Inspect the rocker arm assemblies for an adequate cross section and casting date code. The cross section is adequate if the milled surface for the "foot" does not extend more than 50% of the way through the web on the lower part of the rocker arm as shown in Illustration 1. Using a mirror, arms can be inspected without disassembly.
Illustration 12. Replace all rocker arms with a 4M22 casting date code regardless of cross section.3. Stamp "GL" on the block at the rear of the engine information plate to signify this rework program has been completed. The engine information plate is located toward the rear of the block mid way between the oil pan and the cylinder head. See Illustration 2.
Illustration 2Group 5
8NM20-624
Replace the existing oil pressure alarm switch assembly with a new 1221522 Pressure Switch Assembly.
Group 6
8NM20-1714
Do not remove the rocker stands or injector hold-down bolts. Modify the 1U8013 ( inch drive 5mm hex) to provide a 4.5 to 5 inch long 5mm hex so that injector hold-down bolts can be accessed with the torque wrench without removing the rocker arm stands.
1. Use a torque wrench to tighten each injector hold-down bolt to the high side of the specification (12 +3/-0 N m).