Check the technical condition of the pistons, pins, connecting rods, bearing shells and piston rings, and replace them if necessary.
Before installation, measure the nominal clearance between the piston and the bore in the cylinder block, for which:
- measure the piston diameter with a micrometer at a distance of "A" - 12 mm, from the lower edge of the skirt in a plane at an angle of 90° to the axis of the piston pin measure the diameter of the cylinder mirror in three planes with a micrometer (top, middle and bottom) and calculate the average value;
- subtract the piston diameter from the average cylinder diameter;
- the obtained value of the nominal gap should be within the range of 0.041–0.077 mm, the maximum permissible value, as a criterion for the necessary repairs when parts are worn out, is 0.15 mm.
Wash the new connecting rod bolts, lubricate them with engine oil, insert them and, using the "00.9.120" or "11.2.110" tool – a torque wrench with a protractor – tighten the bolts in three parallel steps on each bolt:
- 1st step tighten to 5.0 Nm (0.5 kgf·m);
- 2nd step tighten to 20 Nm (2.0 kgf·m);
- 3rd step, turn it at an angle of 70°.
After carrying out work that causes changes in the piston bottom protrusion above the mating surface of the cylinder block, it is necessary to re-determine the thickness of the sealing gasket in the following order:
- install a pointer indicator with a measuring block, device "00.2.530" (fig. 6.87, a) on the cleaned surface of the cylinder block and set the indicator to zero;
- set the piston to a position close to TDC;
- install the "00.2.530" device on the cleaned surface of the piston at two measurement points (1 and 2, Fig. 6.87, b), by turning the crankshaft by the vibration damper bolt, take the maximum readings of the indicator at the highest point of piston lift;
- draw and record the piston bottom protrusion at points (1 and 2) for all six pistons;
- the largest value out of 12 measurements determines the thickness of the sealing gasket (1, see Fig. 6.3) cylinder heads;
- if the piston protrusion is 0.92–1.03 mm, install a gasket with two holes; if the piston protrusion is more than 1.03 mm, install a gasket with three holes.
Install the stiffener insert (23, see Fig. 6.2) according to its marking, the arrow points towards the timing drive.
(Information taken from this resource: «BMWman.ru»)