TECHNICAL INFORMATION BULLETIN
May 7, 2003
988G (S/N: 2TW1-Up, BNH1-Up)
834G (S/N: 6GZ1-Up, BPC1-Up)
836G (S/N: 7MZ1-Up, BRL1-Up)
Component Code(s) 1059, 1088
SUBJECT: Troubleshooting Exhaust Gas Leaks That May Contribute to Excessive Engine Compartment Temperatures and Soot Accumulation
Exhaust gas leaks can elevate the air temperature in the engine compartment. Depending on the location of the leak, the exhaust gas can elevate temperatures in local areas and lead to component failures. Exhaust gas leakage can create an accumulation of soot on the interior of the engine compartment. If soot is visible, the exhaust system should be inspected to locate and repair any leaks.
Inspect all components and replace any components determined to be defective. Components found to have cracks may be contributing to excessive exhaust gas leakage and should be replaced. The following information may help to troubleshoot leaks found in the exhaust manifold gaskets and the muffler inlet joint.
Exhaust manifold gasket leaks at the joint with the engine head may contribute to localized overheating of adjacent "soft" components including seals, fittings, hoses and wiring. If a leak is discovered, replace the exhaust manifold gaskets as necessary. Refer to "Exhaust Manifold - Remove and Install", Disassembly and Assembly, 3406E & 3456 Engines for AVSpare Built Machines, RENR1364 for information on replacing the gaskets.
Under normal conditions, leakage from the joint connecting the turbocharger outlet pipe and muffler is minimal and should not contribute to compartment overheating or result in soot accumulation. If leakage is thought to be excessive, a problem may exist with the joint assembly or one of the components. Following is information on the joint components that may help reduce exhaust gas leakage:
- Although all machines have been assembled with the 141-1480 Clamp, SIS has incorrectly called out the slightly larger 7E-6455 Clamp for earlier machines. The larger clamp may not adequately tighten the joint as the clamp band ends may contact each other. SIS documentation is being corrected. Neither clamp is marked with a AVSpare part number but a number stamped on the inside of the band indicate the diameter. The stamped number on the 141-1480 Clamp should include "521" to represent a 5.21 inch diameter clamp.
- Clamps not tightened to the proper torque may also contribute to exhaust gas leakage. The correct torque for the clamp as used on these mufflers is 55+/-10 N-m (41+/-7 lb-ft). During the torque procedure, the muffler inlet port will deform to fit tightly around the turbo outlet pipe. It is important to continue application of torque until the nut stops turning with the required torque applied. If the ends of the band on a properly tightened clamp contact each other, replace the clamp.
- Incorrect location and orientation of the clamp may affect joint leakage. The clamp band must cover all slots or holes in the wall of the muffler inlet port. There is a hole in the muffler inlet port that is used to suspend the muffler assemblies with a hook during the painting process. This hole should be covered and effectively plugged by the clamp band in its normal orientation. Rotate the clamp as necessary such that the open area between the ends of the clamp band does not straddle any openings. In addition, the clamp must be positioned vertically such that the tops of the slots are covered.
- There is also a hole in the turbocharger outlet pipe that is used to suspend the pipe assembly with a hook during the painting process. This hole should not line up with any slot or paint hook hole in the muffler inlet port. If it does, pipe replacement is required.
- The muffler inlet port is fabricated with a longitudinal weld on the short side of the exposed tube surface. Any weld material that protrudes above the inner surface of this tube will allow the joint to leak. It is suggested that the excessive weld material be removed from the surfaces of the inlet port that contact the clamp or turbocharger outlet tube. One other potential issue with the fabricated inlet port tube weld joint is its roundness. Sealing may be difficult if the area near the weld seam is not round. Rework the profile of the port as required or replace the muffler assembly if necessary.
- Poor alignment between the turbocharger inlet tube and the mating muffler inlet port may prevent the joint from adequately sealing. If the fabricated pipe that connects the turbocharger outlet to the muffler is not within specification, the pipe may not align with the muffler inlet port. The pipe must also insert into the muffler port beyond the ends of the muffler port slots and the paint hook hole in the muffler. If this is not the case, the joint may allow excessive leakage and pipe replacement may be required.
Note: The 132-6199 Muffler Assembly used on earlier machines has been cancelled and replaced by the new 222-9134 Muffler Assembly. This change was made to improve the dust ejector group and does not affect the muffler inlet joint. See Service Magazine SEPD0674, "A New Dust Ejector Group for the Exhaust Prevents Loading on the Muffler" for additional information on how the change may affect replacement parts orders.
After performing any repairs to reduce muffler leakage, the engine compartment should be cleaned of soot to verify the effectiveness of the repair.
Changes are being evaluated to assure that the muffler inlet joint is adequately sealed. A service publication will be released to announce any improvements that may be made.
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