1985/06/03 Caterpillar

D379, G379, D398, G398, D399, G399 Engines

SUPPLEMENT: 12/16/85

SERVICE MAGAZINE, JUNE 3, 1985, PAGE 10, "New Crankshaft Seals Used". The illustration that follows clarifies the machining dimensions of the pilot sleeve. The outside diameter of the pilot sleeve was omitted in the above article.

Cross section of pilot sleeve.

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Description of Change: New seals are used at the front and rear of the crankshaft on the above engines. The new seals give improved sealing and longer life. The thrower and baffle used on earlier engines are no longer used.

The new seal is quite different from the former seal because of the hydrodynamic grooves in the sealing lip of the new seal. These grooves move lubrication oil back into the engine crankcase as the crankshaft turns. Because of this design, the front seal group is different from the rear seal group. The installed position of the seal lip grooves is important because the grooves are very sensitive to the direction of crankshaft rotation. If a seal group is installed on the wrong end of the engine, lubrication oil can actually be taken out of the engine because the grooves in the seal lip are in the wrong direction in relation to crankshaft rotation.

Adaptable As: The new seals are in effect as listed in Chart A. They are adaptable to all earlier listed engines.

Four different crankshaft conversion seal groups are available for earlier engines. Two groups are available for the front and two are available for the rear, depending on engine rotation. See Chart B. Use Special Instruction SMHS8301-01 for installation instructions and for special handling requirements. Also, add a note to the Special Instruction referring to this article.

In addition, either a new adapter for the damper must be used, or the former adapter can be reused if a sleeve is installed on it. If desired to install a new damper adapter, see Chart C.

Modification Procedure To Reuse For Former Damper Adapters

It may be economical to reuse the former damper adapter. This can be done by machining a pilot sleeve and installing it on the former adapter. See illustration. The sleeve is required to provide a pilot on the crankshaft flange for the former adapter. These former adapters are machined to pilot (or fit) inside the oil thrower, but the thrower is not used with the new seal. The damper adapter must be centered on the crankshaft flange to provide the desired dampening action from the damper.

Machining and installation of pilot sleeve if former adapter reused.

Heat the mild steel sleeve to 180°C (350°F). Press it on the former adapter to a distance of 19.0 mm (.75"). After installing the new seal parts, install the former adapter and sleeve on the end of the crankshaft.