Usage:
See The Chart For Models
- SUPPLEMENT: 08/25/80
SERVICE MAGAZINE, SEPTEMBER 10, 1979, PAGE 6. In the article "Pin Bore Is Now Offset (Not In The Center) .059" (1.5 mm) In The Piston To Stop Vibration Of The Cylinder Liners Which Can Cause Pitting On The Coolant Side Of The Cylinder Liners" on Page 6, a wrong part number is shown in the parts chart. Change the last item at the bottom of the chart to read: "9S7788 -- Ring (Oil) -- 9S7788".
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- SUPPLEMENT: 01/28/80
SERVICE MAGAZINE, SEPTEMBER 10, 1979, PAGE 6. In the article "Pin Bore Is Now Offset (Not In The Center) .059" (1.55 mm) In The Piston To Stop Vibration Of The Cylinder Liners Which Can Cause Pitting On The Coolant Side Of The Cylinder Liners" a wrong model is shown in the bottom section of the parts chart. Change "235 Excavators" to read: 225 Excavators.
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Description of Change: The pin bore in the piston is now offset .059" (1.5 mm) to prevent vibration of the cylinder liners on the models shown in the chart. Maximum vibration of the cylinder liner is during the period when the piston moves from side to side as it goes through the top center position. The piston with the offset pin bore will pass through the top center position in a more smooth motion. Excessive (too much) pitting is possible when vibration causes corrosion to fall off of the coolant side of the liner. High frequency vibrations can also cause pitting on the coolant side of cylinder liners which do not have corrosion.
Pin bore is offset .059" (1.52 mm) as shown.
Regular cooling system maintenance is necessary with both the new and the former pistons.
The coolant must prevent rust and pits in the cooling system. For this reason, water is not a good coolant. All water can cause corrosion. Both distilled water and softened water that do not have corrosion inhibitors in them become seriously acidic very rapidly.
Always add Caterpillar corrosion inhibitor to the water anti-freeze mixture at the time of the initial fill of the cooling system. If water only is used, it is most important for corrosion inhibitor to be added. Use 3P2044 Corrosion Inhibitor. (Do not use liquid Caterpillar cooling system inhibitors with Dowtherm 209.)
The amount of liquid corrosion inhibitor used in the original fill of a cooling system must be 3% to 6% concentration. Too much corrosion inhibitor in a coolant mixture can cause an overalkaline condition that can damage metals such as aluminum or the solder used in the construction of cooling system components.
Adaptable As: Direct replacement. There is no weight difference between a new and former piston. It is possible to use both the new and the former pistons in the same engine. But it is our recommendation to use all new or all former pistons in an engine.
The same compression ring and oil rings are used on both the new and former pistons.
