BOLT 7X2584 - Caterpillar

3406B Truck EnginesReference: ..."Know Your Cooling System", SEBD518-04. ..."Operation And Maintenance Management Guide", SEBU6026 for 3406B Truck Engines.
..."Operation And Maintenance Management Guide", SEBU6107 for 3406B Truck Engines with PEEC.
Description of Change: A new water temperature regulator manifold (housing), new housing cover, and new inlet adapter on the water pump are used on all 3406B Truck Engines. These three parts have less copper in the aluminum to reduce the possibility of erosion and galvanic corrosion. The parts are therefore more tolerant to incorrect electrical grounding and to poor cooling system maintenance.Also, the new pump adapter has a smaller pilot diameter and relocated forcing screw holes to prevent it from being broken when removed.
Adaptable To: The new parts are effective with the serial numbers listed in the chart. They are directly adaptable to earlier 3406B Truck Engines, either individually or all used together. The lower copper content in the new parts will NOT ELIMINATE problems of erosion and/or galvanic corrosion caused by poor cooling system maintenance and/or incorrect electrical grounding. Refer to the Reference Publication and to the following topic.
Grounding Of The Truck Electrical System
A lack of correct grounding circuits results in stray voltages caused by electrical current seeking ground through a path other than the desired ground path. These stray voltages can create voltage potentials in the engine coolant. This causes electrolysis in the coolant and thus galvanic corrosion of dissimilar materials that are fastened together. As more use is made of lighter materials in engines, the chance of galvanic corrosion increases if these materials are connected to a ground wire.
For example, in some cases it has been a practice to ground the alternator to the temperature regulator housing on 3406B Truck Engines. This usually causes electrical current to flow through dissimilar materials-from the aluminum housing into the iron cylinder head. The difference in materials plus the current flow immediately causes galvanic corrosion and deterioration of the aluminum housing. Even though the ground wire is connected to a stud or bolt installed through the housing into the cast iron head, a poor ground will occur because of oil or compound on the threads.
Alternators should be grounded by running a cable directly from the alternator ground terminal to the truck frame or battery negative circuit. The alternator can be grounded to the engine block if the block is grounded to the frame or battery negative circuit. Also, connect a 14 gauge wire for the ground on the fuel shutoff to the frame or the block-not to a mounting bolt or stud on the shutoff.
Proper Cooling System Maintenance
New parts and proper electrical grounding will not prevent erosion caused by underconcentration of antifreeze and cooling system conditioner. It is imperative that the cooling system be properly maintained. Review and follow carefully the details in the appropriate Operation And Maintenance Management Guide referred to at the beginning of this article.