Usage:
3406, 3408 Truck Engines
A .060" (1.52 mm) diameter orifice is machined in each of the two oil supply passages to the seal area in the BrakeSaver stator. These orifices prevent possible high oil pressure against the seal, especially during cold starts. Too much oil pressure can cause seal leakage and/or possible seal damage.
To machine the orifice, each passage is drilled with a larger size (.125" -3.18 mm diameter) drill to a specific depth, then the .060" (1.52 mm) diameter drill is used to cut the orifice opening. Because of casting and machine tolerances, some stators have been found where the larger drill cut all the way through, and there was no orifice opening in one or both passages. For this reason, the depth of the larger drilled hole has been changed to make sure there is enough material in the passages for the orifices. See the illustrations for location of the two oil supply passages and the machined orifices.
Location of oil passages in BrakeSaver stator.
Location of machined orifice, orifice plug installed as a factory modification, and 4J9780 Orifice Plug installed as a field modification.
At the factory, a modification has been made to install orifice plugs in all stators that do not have machined orifices. The plugs are installed in a different location as shown. Orifice plugs can also be installed as a field modification in any stators that do not have either machined orifices or the factory modification. If any of these stators are in the field, they will be found only in 3406 Engines 92U5186-9331 and 3408 Engines 28V171-661 equipped with BrakeSavers. It is not necessary to make an inspection of these engines, but check the stator on any engine that has a problem of oil leakage at the BrakeSaver seal. Engines with the factory modification have a "BS" mark on the identification plate after the serial number.
Be sure to check both oil passages in the stator, because each must have an orifice. If a passage does not have either a machined orifice or a factory installed orifice plug as shown in the illustrations, drill the hole to a diameter of .250" (6.35 mm), .56" (14.3 mm) deep and cut 1/16-27 NPT threads in the hole. Then install a 4J9780 Orifice Plug as shown. Be sure the threads are deep enough so the head end of the plug does not extend above the machined surface of the stator. This will give the needed restriction to the flow of oil. Before installation in the engine, thoroughly clean the stator to remove any metal particles or other foreign material.