Attention! Be careful when installing pistons and connecting rods. so as not to damage the oil nozzles for cooling the pistons, if any on this engine. The manufacturer recommends that after reinstalling the piston group, adjust the position of the injectors using tool BMW 117 320 (engine M43TU) or 119 370 (N42 engine).
Insert selection
1. Shutter BMW produces connecting rod bearings in several sizes: nominal size for standard crankshafts and repair sizes for shafts with machined journals.
2. Pass the crankshaft to the service station specialists - they, if necessary, will machine it and select the liners of the required size.
Installing pistons with connecting rods
Note. For assembly, you need new bolts for fastening the covers of the lower heads of the connecting rods. This operation will also require a piston ring compression tool.
3. It is assumed that the main bearing covers are already installed (see paragraph 17).
4. Insert the connecting rod bearing shells into place. Make sure that the lugs of the liners fit into the corresponding grooves of the connecting rod heads and their caps. Do not touch the working surfaces of the earbuds with your fingers. If the earbuds are coated with protective grease, wash it off with kerosene. Wipe the earbuds dry with a lint-free cloth.
5. Lubricate the surfaces of the cylinders, pistons and piston rings, then lay out the pistons with connecting rods in the order in which they were installed.
6. Begin installation with cylinder #1. Make sure the piston rings are in place and spaced as shown in paragraph 16. After that, put a mandrel on the top of the piston and squeeze the rings with it.
7. Insert the piston with the connecting rod from above into cylinder #1. Rotate the assembly so that the arrow on the piston head points towards the front of the engine (those. towards the chain), and the marks on the lower head of the connecting rod and on its cover - towards the exhaust manifold. Use a hammer handle to drive the piston into the cylinder until the piston crown is flush with the plane of the cylinder block (pic. 18.7, a, b).
8. Be convinced that loose leaves of the lower head of a rod and its covers are on the places. Lubricate the crankshaft crank and both bushings with engine oil. Push the piston with the connecting rod down and put the bottom end of the connecting rod onto the crank. During this operation, be careful not to scratch the cylinder mirror with the connecting rod. Install the cap on the bottom end of the connecting rod. Keep in mind: the protrusions of the liners of the connecting rod and the cover must face the same direction.
9. Screw in new bolts of fastening of covers and gradually, in turn tighten from the moment corresponding to the 1st step of an inhaling (see technical data). After tightening both bolts to the torque corresponding to the 1st stage, tighten them to the angle corresponding to the 2nd stage. To turn the bolts to the required angle, it is recommended to use a special wrench with an angular scale. If there is no such knob, apply white paint marks on the head of the bolt and on the connecting rod cover, by which it will be possible to control the angle of rotation of the bolt.
10. After tightening the connecting rod head bolts, rotate the crankshaft. Check if it rotates easily. After installing new parts, the shaft may turn tighter than usual, but the resistance to rotation should be uniform, without local jamming.
11. Install the remaining pistons with connecting rods in the same way.
12. Install an oil damper on the underside of the engine (if provided by design).
13. On a 4-cylinder engine, install the cylinder head, balance shaft housing with oil pump and sump (see chapter 2A).
14. On a 6-cylinder engine, install the cylinder head, oil pump and sump (see chapter 2B).