Inspecting, Maintaining and Repairing Connecting Rods

Figure 3-26.–Removing or installing a piston pin bushing. When you insert new bushings, be sure that the bore into which they are pressed is clean and that the oil holes in the bushing and the oil passages in the rod are aligned. To obtain proper clearance, sometimes you will need to ream a piston pin bushing after it has been installed. Figure 3-27 shows equipment used to ream a bushing. After installing a new bushing, check the alignment of the rod with equipment such as illustrated in figure 3-28. Be sure to check the manufacturer’s technical manual for details concerning clearances and alignment procedures. INSPECTING, MAINTAINING, AND REPAIRING CONNECTING RODS Most connecting rod troubles involve either the connecting rod bearing or the piston pin bearing. You can avoid these troubles by performing proper maintenance procedures and by following instructions in the manufacturer’s service manual. There are, however, certain unavoidable troubles, such as cracked connecting rods caused by defective material. Such cracks must be discovered before they develop to a point that the rod fails. Magniflux testing is considered the best method for locating cracks. If you discover a crack in a connecting rod, replace the rod; do not try to repair it. If you have to replace a damaged rod, send it, with other damaged parts, to a salvage center for possible reclamation. Do not repair defective connecting rod bolts, except for removing small burrs by using a fine rectangular file. If you doubt the condition of a bolt or a nut, replace it. Check the connecting rod bore for out-of-roundness with an inside micrometer. Make the correction and recheck the bore. If the distortion is permanent, replace the rod. You can make plugged oil passages of connecting rods serviceable by running a wire through them. In extreme cases, you may need to drill the passages free of foreign matter. Figure 3-27.–Reaming equipment. 3-18