LONG BLOCK M 20R7051 - Caterpillar

recommendations are to use anti-seize thread compound on bolts in many applications, especially bolts for main and connecting rod bearings. The use of this compound is important to prevent thread seizure and damage, but it can cause other problems. For example, high levels of copper in S.O.S. (Scheduled Oil Sampling) tests have been caused by the use of too much 5P3931 Anti-Seize Thread Compound on main and connecting rod bolts. This anti-seize compound has copper particles in it. To prevent this problem, the recommendation is to use 2P2506 Anti-Seize Thread Compound in place of the 5P3931 Compound. The 2P2506 Compound does not have copper in it, and is now used at the factory to prevent possible problems. If, for any reason, the 5P3931 Compound must be used in a location or compartment where it has contact with oil that will have S.O.S. tests, use very small amounts and make applications carefully.
Correct application of any anti-seize compound is important. In addition to the threads of a bolt, be sure to put the compound on the contact surface of the bolt head. Also, with the use of anti-seize compound, correct bolt torque becomes very important. Since the anti-seize compound lowers contact friction, torque/tension characteristics change, and fastener stresses are increased. If the bolt is tightened to a standard torque, not specifically for use with anti-seize compound, the bolt can be stretched (pulled longer) too much, and possibly broken. For this reason, specific torque values or torque-turn-tightening (T-T-T) procedures are generally used with recommendations for the application of anti-seize compound. Use the Service Manual as a reference for the correct methods and procedures to follow.