FITTING-OUTLET 7W7381 - Caterpillar

3400 Family Of EnginesReference: Engine News, October 1991, Page 5, "No Gaskets Used With Aluminum Flywheel Housings."Oil leakage at the flywheel housing to block joint can be a result of high pressure oil leakage past a core plug in an oil gallery. This core plug is at the rear of the block and the end of the main oil gallery. If inspection indicates oil is leaking past the core plug, a new 100-7399 Plug and 3E6747 O-Ring Seal can be installed in place of the 2M6471 Core Plug. This will help prevent oil from leaking out of the end of the main oil gallery. Use the procedure that follows to install the new plug and O-ring.
1. Remove the 2M6471 Core Plug from the end of the main oil gallery. Make sure the bore is free of burrs.2. Install the new 3E6747 O-Ring Seal on the new 100-7399 Plug. Lubricate the seal with clean engine oil. Carefully install the plug and seal (chamfered end first) into the oil gallery bore by hand until the press fit is encountered.
Location of components. Rear face of cylinder block (A). Main Oil Gallery (B). 2M6471 Core Plug (1). 100-7399 Plug (2). 3E6747 O-Ring Seal (3).3. Complete the installation by using a driver to press the new plug and seal into the oil gallery until the plug makes full contact with the shoulder in the bore.The new plug and seal will be trapped in the gallery when the flywheel housing is installed.
This plug is adaptable to all engines using either a standard gasket or 1U8846 Gasket Maker between the flywheel housing and block. See the Reference Article).
See the appropriate Service Manual Specifications Module for the torque and tightening sequence for the bolts that fasten the flywheel housing to the cylinder block. The correct torque and tightening sequence is important to ensure a leak-free joint.