Figure 54. Piston and connecting rod after disassembly: 1 - piston rings; 2 - piston pin retaining rings; 3 — piston; 4 - piston pin; 5 — connecting rod; 6 - bearing sleeve in the upper head of the connecting rod; 7 — connecting rod bearing cap mounting bolts; 8 — upper connecting rod bearing shell; 9 — lower connecting rod bearing shell; 10 — connecting rod bearing cap
Figure 54 shows individual parts of the piston with the connecting rod. When assembling and installing them, the following operations must be performed:
- before assembly, carefully inspect the piston surfaces (in case new pistons are installed). Check the diameters, size groups and the last two digits of the spare parts catalogue, which must be indicated on the pistons and comply with the installation requirements;
- when replacing connecting rods, pay attention to the lower parts of the bearing caps, where one or two dot marks may be punched, which determine the size group of the bearing liners;
Figure 63. Piston with connecting rod assembly
[Publication taken from an online resource www.mercedesman.ru]
- lubricate the piston pin and press it into the holes of the piston bosses and connecting rod bushing using a mandrel of suitable diameter. Install the piston pin retaining rings on both sides, making sure they are seated properly in their grooves. The piston with the connecting rod should be installed in the engine in such a way that arrow 1 (figure 63) on the piston bottom pointed to the front of the engine, and the guide petals of the 2 connecting rod bearing shells were located on the left side of the engine;
- make sure that after assembly the piston rotates freely in both directions on the piston pin;
Figure 64. Piston rings in section: 1 - composite oil scraper ring with expander (the working surface is chrome plated); 2 - lower compression ring with a trapezoidal cross-section; 3 - upper compression ring of square section (the contact surface is asymmetrically ground and chromed)
- using piston ring pliers, install the rings on the piston, paying particular attention to the correct sequence of their installation. Compression rings can be easily mixed up, so pay attention to their cross-sections and location on the piston. Figure 64 shows the sections of the rings and the order of their arrangement.