VALVE GP-RELIEF 9T7389 - Caterpillar

Definition
The exhaust ejector is a device used to remove excess dirt from the precleaner. This is accomplished by passing the dirt out via exhaust gases.
Operation
The exhaust ejector removes the excess dirt by applying a suction to a fitting in the side of the precleaner. This suction is developed by exhaust gas rushing through a nozzle or, in later years, through a triple lobed venturi. The dust is removed from the "floor" of the precleaner, sucked through the exhaust tube (hose), then exhausted out the stack.
There are two types of design relationships between the dust ejector tube and the venturi. One type is completely self contained in the muffler or stack such as the 140G (Illustration 2) or the early D10 (Illustration 3). The other type has the dust tube welded into the muffler with the venturi in a separate exhaust stack such as the 970F or D8N (Illustration 4).
The self contained type usually is trouble free, except when damaged either by vibration or external bumps. The center tube is usually not in the correct position after this occurs.
The two piece system will not operate properly when the two pieces, muffler and exhaust stack, are not assembled to the proper engagement length. THIS ENGAGEMENT LENGTH IS CRITICAL! The position of the tube, that extends out of the outlet pipe of the muffler, must extend up into the stack until the outlet of the dust tube is in a special position relative to the narrowest portion of the nozzle or venturi. This is the point which creates the highest vacuum and varies with ejector stack nozzle design.
If the ejector is the 360 degree cone type, the position for the end of the dust tube relative to the narrow throat is about 6.0 mm (.25 in) above the throat (downstream). See Illustration 1. If the ejector is the triple fluted design, then the outlet of the dust tube needs to be positioned 25 to 30 mm (1.0 to 1.2 in) below the narrowest portion of the flutes (upstream). All newer pipes have the triple flute design. Look into the end of the pipe to see which type of nozzle you have. See Illustration 1.
Illustration 1. (A) End view of triple fluted ejector. (B) End view of 360 degree cone ejector.To check this relationship, convenient tools for determining the position of the nozzle include the 9U-5155 O-Ring Sizer or a large socket with an extension.
Mufflers, which are equipped with a dust ejector tube and need an exhaust stack to supply the venturi, are now manufactured with two small rectangular lugs on the outside of the outlet pipe. These lugs are the STOPS for the exhaust stack. The stack should be driven on until the bottom edge of the stack contacts the lugs. This provides for proper muffler/stack engagement and thus dust tube/venturi relationship (Illustration 4).
The stacks are also manufactured with rectangular lugs on the outer skin. These lugs are to ease assembly and disassembly of the stack to the muffler. This provides