SEAL-BUFFER 1506738 - Caterpillar

D379, D398 and D399 Industrial, Marine and Generator Set Engines So EquippedThis information gives a description of some possible service problems for shut-off groups and the solutions for these problems.
PROBLEM: Shut-off control group does not work correctly; will not shut-off engine.
It is possible that there is too much end clearance of the carrier assembly in the shut-off control pump group. This will permit the tangs on the 5N2710 Washer to move out of the slots in the cover assembly and prevent shut-off of the engine. If there is enough clearance to permit the installation of another 1K502 Washer, it can be installed on the shaft next to the existing 1K502 Washer. See Illustration 1.
Illustration 1. Location of washers in oil pump group.On Page 4-8 of the Service Manual for D379, D398 and D399 Industrial and Marine Engines, Form SEBR0511, a specification is shown of 0.051 to 2.03 mm (.020 to .080") for the end clearance of the shaft. This end clearance specification is no longer used. Make a note of this in your Service Manual.
PROBLEM: Air shut-off group does not completely close air intake.
The most common cause of this problem is corrosion or deposits between the 3N8915 Shaft and the 3N8911 Housing. This corrosion prevents complete rotation of the shaft. The 5N3279 Cover Assembly can be removed and a penetrating type oil put on the shaft. Gradually move the shaft in clockwise and counterclockwise directions until the shaft moves freely. See Illustration 2.
To make sure the air shut-off group operates correctly, it must be checked every 500 SMU as shown in the Operation and Maintenance Guides or Owner's Manuals.
In engines equipped with hydraulic activated air shut-off groups, another possible cause is an alignment problem of the hydraulic cylinder. This can be caused by the part number which extends above the surface of the 5N9202 Flange. The part numbers can be removed with a file. This part number is only a problem on some early flanges. See Illustration 2.
Illustration 2. Location of parts in shut-off control group.PROBLEM: Oil leakage past the 7L6597 Lip-Type Seal in pressure control valve group.
This can be caused by a bent 5N4724 Valve (stem). The valve can be bent if the hydramechanical unit is lifted or held (carried) by the emergency shut-off knob.
The lip-type seal can also be damaged when the 5N4725 Adapter is loosened for removal of the valve assembly. The lip-type seal is located inside this adapter and can be cut by the threads behind the 6F612 Nut on the valve assembly. To prevent this, the nut can be completely loosened and moved to the groove at the ends of the threads, before the 5N4725 Adapter is loosened. When the valve is installed, tighten the 5N4725 Adapter first. Then tighten the 6F612 Nut back into its original position, against the knob. See Illustration 3.
The inner and outer rotors of the 5N2712 Gerotor Assembly are made as a complete set. Because of this, a replacement of both the inner and outer rotors must always