GUIDE AS 9R8724 - Caterpillar

Corrosion in sea water circuits can result in premature deterioration of system components, leaks, and possible cooling system contamination.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 within 24 hours of initially filling the plumbing with sea water. If no significant corrosion is noted, inspect the zinc rods weekly or inspect the zinc rods after each 50 hours of engine operation.Note: Caterpillar requires the inspection of the zinc rods every 50 service hours until a wear rate is established.Locations of the Zinc Rods
The number and the location of the zinc rods may vary between engines.
Illustration 1 g01937142
One zinc rod is located on top of the auxiliary water pump.
Illustration 2 g02158846
Three zinc rods are located on the aftercooler.
Illustration 3 g01937141
One zinc rod is located in the intake for the heat exchanger. One zinc rod is located in the outlet for the heat exchanger.
Inspect the Zinc Rods
Remove the zinc rod.
Illustration 4 g00104048
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 5 g00104049
Unscrew the old zinc rod or drill the old zinc rod from the plug. Clean the plug.
Apply 9S-3263 Compound to the shoulder of a new zinc rod with pipe threads. Do not apply the compound to any other type of zinc rod. Apply the compound only to the shoulder of the zinc rod. Install the zinc rod into the plug.
Coat the external threads of the plug with 5P-3413 Pipe Sealant. Install the zinc rod. Refer to the Specifications Manual for more information on torque specifications.