Checking the clearance between the bearings and the connecting rod journals of the crankshaft (BMW 5 Series E12)

Insert the pistons into the cylinders (without piston rings) with connecting rods in accordance with the cylinder number marks on the piston bottom (the count is carried out from the camshaft drive side). In this case, the arrow on the bottom for orienting the piston in the cylinder must be directed towards the camshaft drive.

Install the connecting rod cap by placing a piece of plastic gauge wire type PG 1 between the unlubricated bearing shell and the connecting rod journal.

Tighten the nuts of the connecting rod cap mounting bolts to a torque of 5.2-5.7 kgf·m. Remove the cap and, using the scale on the packaging and the flattening of the wire, determine the gap size.

Remove the pistons with connecting rods through the cylinders.

Insert the piston rings into the cylinders and check the gap in the piston ring lock with a set of feeler gauges. Check the gap between the piston rings and the grooves with a set of feeler gauges, inserting the ring into the corresponding groove and observing their orientation (see photo). If the ring has a TOP mark ("Top"), then install the ring with the mark facing up (to the piston bottom).



Lubricate the piston grooves and piston rings with engine oil and install the rings on the piston, arranging the ring joints at 180° intervals.



Compress the piston rings with a mandrel and insert the pistons with connecting rods into the cylinders, having previously lubricated their walls with engine oil (point the arrows on the piston bottom towards the camshaft drive).

Lubricate the connecting rod bearing shells and connecting rod journals with engine oil. Install the connecting rod caps on the crankshaft journals and tighten the connecting rod bolts to a torque of 5.2-5.7 kgf·m.

Install the oil pump, paying attention to the tension of the drive chain (the adjusting shims must be installed in the position shown in the photo so that they do not block the main oil line). The chain should bend slightly when you press with your thumb in the middle of the chain branch.

Note: If the correct chain tension cannot be obtained by removing or installing additional adjusting shims, replace the chain, which is supplied in two lengths (for models "518" and "520"): chain with a red mark - normal length; chain with a green mark - increased length.

Perform the final tightening of the oil pump mounting bracket bolts only at the end of the operation, so as not to create stress in the pump body.

Install the oil pan.

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