HOSE AS 3492705 - Caterpillar

Introduction
The problem that is identified below does not have a known permanent solution. Until a permanent solution is known, use the solution that is identified below.Bearing discoloration is a natural phenomenon given the material and the process used in the manufacture of engine bearings made of lead, tin, and copper. These bearings can range in color from a bright silver color when new to a dark gray when fully aged. Bearings remain fully functional through the full range of the color transformation. The purpose of the Technical Information Bulletin is to report the acceptability of bearings at all stages of the aging process and to provide dealers and customers the description of other types of bearing stain. Most other bearing discolorationes are not harmful to performance. However, for stains that result from corrosion of the bearing material, the effect on performance or life expectancy is to be determined. The following information is provided in order to assist in your evaluation of bearings that are exhibiting stain or corrosion.Problem
Engine connecting rods and main bearing with a material code of 5 or 8 may not have uniform color on the inside diameter of the bearings. Refer to Illustration 1. There are three different types of discoloration:
Gray
Brown
Any discoloration in addition to graySolution
Refer to the different types of discoloration and the illustrations below in order to determine if the bearing is acceptable.Gray Discoloration
The intensity of gray on some connecting rods and main bearings is caused by the variation in thickness of the tin flash that is electroplated onto the bearings. The flash protects the steel back of the bearings from corrosion. The bearings have a specification of thickness that requires a maximum of 2.5 microns. If the thickness is 0.5 microns or less, the lead-tin overlay will penetrate through the tin flash. This will cause the intensity of the color to vary. Gray discoloration has no effect on the function of the bearing. Bearings that have a gray discoloration are acceptable to use.Note: Given sufficient time and temperature, the tin flash material will diffuse into the overlay material that the tin flash initially covered. This diffusion is a natural ageing process.Brown Discoloration
The brown discoloration is caused by a chemical reaction between condensation and deposits on the surface of the bearing. This may lead to corrosion on the bearing surface. Bearings that display brown discoloration should not be used. Refer to the illustrations below.Summary
Do not use the bearing:
Bearings that have areas of brown discoloration
There is a sharp, distinct boundary between light gray areas and dark gray areas.
Any purple areas or blue areas on the bearingNote: Do not confuse brown discoloration with a rust preventive that is applied at the supplier. The rust preventive adds additional corrosion protection during shipment. Follow the cleaning procedure in Reuse and Salvage Guideline, SEBF8009 in order to determine if the discoloration is a rust preventive.Bearings that are suitable for use
Bearings with gray discoloration that change in intensity from light gray to dark gray without a sharp, distinct boundary
Discoloration