Missing Rear Gear Train Idler Shaft Mounting Bolt Seals May Result In Oil Leaks Caterpillar

THIS TIB REPLACES THE JANUARY 21, 1998 EXCAVATOR TIB, COMPONENT CODE 1165, "MISSING REAR GEAR TRAIN IDLER SHAFT MOUNTING BOLT SEALS MAY RESULT IN OIL LEAKS". DESTROY THE JANUARY 21, 1998 TIB. IT WILL NOT APPEAR IN THE SEMI-ANNUAL INDEX.

Problem:

The above 350 and 350D Excavators were built with a 4P-2704 Rear Gear Group inside the rear PTO flywheel housing which includes two idler shafts bolted to the 1 inch thick housing plate attached to the rear of the cylinder block. The tapped holes in the plate are drilled through the plate. Due to the design of the pressure oil feed supplying oil to the idler gear bearings, oil may flow through the metal to metal joint between the shaft and the plate and leak out the front of the plate past the bolt threads. This can create a visible oil leak. Since there are two shafts, the oil leak may occur on either or both sides of the front of the flywheel housing plate.

There have been three different designs of the idler shaft since first production of the 350 and 350L Excavators.

* The initial design, Part Number 4P-2473, did not have any provisions for an O-ring seal to prevent the pressurized oil from traveling through the bolt threads.

* The second shaft design, Part Number 113-5343, provided a single O-ring groove for used with a 6F-4855 O-Ring Seal around the bolt hole located closest to the pressure feed hole in the center of the shaft. This was an attempt to stop the oil leakage.

* The third design, with O-ring seals around both bolt holes and shaft Part Number 160-7563, was never effective in production on the 350 (2ZL, 7RK, 8HK) Excavators or the 350L (9DK, 3ML) Excavators. This design was effective just prior to the end of production in July 1998 with 350L (9FL) Excavators powered by 3306 (13Z42935-Up).

Solution:

There are two legitimate fixes for the oil leakage problem at the bolt threads in the plate.

* The 160-7573 Shaft may be installed at the two locations in the rear gear train using two 6F-4865 O-Ring Seals. Implementing this improvement will result in significant downtime for the machine.

* A preferable fix, which will require minimal downtime, and may even be done in the field, is to use epoxy to seal the tapped hole openings in the front of the flywheel housing plate. See the following procedure:

Parts Needed:

143-9508 Epoxy

143-9509 Mixing Nozzle

4C-4079 Cleaner (aerosol can) or 9U-6346 Cleaner (pump spray)

143-9510 Applicator (includes 143-5911 Plunger)

1. Clean the flywheel housing plate in the area of the shaft bolt holes on both the right and left sides of the engines using the 4C-4079 or 9U-6346 Cleaner. A small brass/wire brush may be needed to remove excessive amounts of oil/dirt build-up. (If you cannot use the 4C-4079 or 9U-6346 Cleaner, use a brake cleaner that does not leave an oily residue.)

2. Use a (black) Scotchbrite pad to remove as much paint build-up or loose paint around the tapped bolt hole openings where the epoxy will be applied. Clean the surfaces thoroughly, then spray a light coat of the 4C-4079 Cleaner on them. Allow the surfaces to dry completely (approximately 5 minutes).

3. For applying the epoxy with the 143-9510 Applicator it is recommended to have a 5/16 inch opening in the applicator nozzle to ensure good coverage. To achieve this, first cut the of the mixer nozzle to increase the orifice size. Then, obtain a 2.5 inch length of 5/16 inch inside diameter clear vinyl hose (cut one end square and the other end at 45 degrees). Attach the square end of the hose to the mixer nozzle.

4. Place the tapered end of the hose flat against the flywheel housing in the area of the bolt holes. Carefully squeeze the trigger for the 143-9510 Epoxy Applicator and apply the epoxy to cover completely the area on and around the bolt holes. Use a clean putty knife to smooth and blend as necessary.

5. Allow the epoxy to set-up for at least 30 minutes (until the epoxy surface in not tacky) before starting the engine. Before putting the excavator back in service, be sure the epoxy has sufficiently cured (firm to the touch).

6. After the epoxy is cured, paint the area of the flywheel housing where the epoxy was applied.

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