①The tightening torque is too large and the force is uneven during assembly. Since there is no strict use of a torque wrench during assembly, and the specific tightening torque is not well understood, I think the tighter the better; a longer force rod is used to tighten the connecting rod bolts, but the tightening torque is too large and exceeds the bolt material. The bearing capacity causes the connecting rod bolts to yield and deform, causing them to break due to excessive elongation under the impact load. It should be emphasized that the connecting rod bolts must be tightened according to the standard. Never think that the tighter and the stronger, the better.
② The connecting rods of diesel engines are divided into various grades. During maintenance, attention should be paid to not replacing connecting rods of different grades. If the connecting rod cover is messed up or installed incorrectly due to carelessness during maintenance, the joint surface of the big end of the connecting rod will not fit tightly. During engine operation, the connecting rod cover will loosen and the connecting rod bolt will break.
③ If the diesel engine overruns or the piston is burned in the cylinder during operation, the connecting rod bolt will be broken. If the engine has an overspeed failure during use, the engine should be inspected and the connecting rod bolts should be replaced; if a serious cylinder pull occurs in an individual cylinder during operation, the connecting rod bolts should also be replaced when replacing the cylinder piston assembly.
④Material problems, processing defects and heat treatment process problems can also cause connecting rod bolts to break during engine operation.
Precaution:
① Every time when running 12,000km for secondary maintenance, the engine oil pan should be disassembled and the use of the engine bearing bushes should be checked. If the clearance of individual bearing bushes is found to be too large, it should be replaced. The connecting rod bolts should also be replaced at the same time. If you find that the engine is not running smoothly or makes abnormal noise during normal operation, you should stop the engine in time for inspection.
② During each maintenance, the newly replaced connecting rod bolts should be inspected. Pay attention to whether there are cracks or dents in the head, guide part, and thread of the bolt, and whether the tooth shape and pitch of the thread are abnormal. If there are any abnormalities, they should be resolutely used.
③ When assembling the connecting rod cover, use a torque wrench and tighten according to the specified standards to prevent the torque from being too large or too small.
④Select connecting rod bolts produced by supporting factories.
