3176B Marine Engine Caterpillar

Corrosion in sea water circuits can result in premature deterioration of system components, leaks, and possible cooling system contamination. The cause for the accelerated corrosion may be the lack of zinc rods in the sea water system.

Zinc rods are inserted in the sea water cooling system of the engine in order to help prevent the corrosive action of salt water. The reaction of the zinc to the sea water causes the zinc rods to deteriorate. The zinc rods deteriorate instead of engine parts for the cooling system that are more critical. Rapid deterioration of zinc rods may indicate the presence of uncontrolled electrical currents from improperly installed electrical attachments or improperly grounded electrical attachments.

The zinc rods must be inspected at the proper intervals. The zinc rods must be replaced when deterioration occurs.

Inspect the Zinc Rods

The zinc rods are red for easy identification. Table 1 shows the locations of the zinc rods and the quantities of the zinc rod:

Table 1

Locations of the Zinc Rods
Location	Quantity
Right Heat Exchanger Bonnet	2
Left Heat Exchanger Bonnet	1
Raw Water Pump Elbow	1

1. Remove the zinc rod.

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Illustration 1	g00104048

2. Tap the zinc rod lightly with a hammer. If the zinc rod has deteriorated, or if the zinc rod flakes, install a new zinc rod.

Replace the Zinc Rods

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Illustration 2	g00104049

1. Unscrew the old zinc rod or drill the old zinc rod from the plug. Clean the plug.

2. Apply 9S-3263 Compound to the shoulder of a new zinc rod. Apply the compound only to the shoulder of the zinc rod. Install the zinc rod into the plug.

3. Coat the external threads of the plug with 5P-3413 Pipe Sealant. Install the zinc rod. Refer to Operation and Maintenance Manual for more information on torque specifications.