HEAT SINK AS-POSITIVE 9Y7173 - Caterpillar

3208 EnginesA high concentration of aluminum in an engine oil analysis is not necessarily an indication of engine damage on 3208 Engines. The engine rocker arm assembly has thrust washers next to the aluminum support brackets which hold the rocker arm shaft. Normal contact of the thrust washers against the aluminum brackets during engine operation can wear away some of the aluminum from the brackets. This causes very small particles of aluminum in the engine oil, especially during the first several hours of operation of a new or rebuilt engine. The result is an indication of high aluminum content in an oil analysis.
Make a visual inspection of the oil filter elements to see if the high aluminum content comes from other sources, like pistons or bearings. The aluminum worn from the support brackets will not generally be visible in the oil filter elements.
Since the amount of aluminum worn from the brackets is very small, it will not cause engine damage if normal oil change recommendations are followed. The wear on the brackets will not have an effect on operation of the engine or valve mechanism, unless the brackets wear enough to permit contact between the rocker arms and the brackets. When the brackets become worn to a depth of approximately 0.89 0.08 mm (.035 .003"), which is the thickness of one thrust washer, a second thrust washer can be installed to prevent rocker arm contact. When the brackets become worn to a depth of approximately 1.78 mm (.070") (the thickness of two thrust washers), install new shaft support brackets.