3176C and 3196 Marine Engines Zinc Rods - Inspect/Replace Caterpillar

Zinc Rods - Inspect/Replace
1.1. Inspect the Zinc Rods
2.1. Replace the Zinc Rods

Corrosion in sea water circuits can result in premature deterioration of system components, leaks, and possible cooling system contamination. The cause for the premature 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 
Left Heat Exchanger Bonnet 
Transmission Oil Cooler 
Fuel Cooler 

  1. Remove the zinc rod.

    Illustration 1g00104048

  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

    Illustration 2g00104049

  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 Special Publication, SENR3130, "Torque Specifications" for more information on torque specifications.