Fig. 91. Measuring the clearance by the height of the piston rings in the piston grooves. All valves must be well cleaned
Fig. 92. Removing carbon deposits from piston ring grooves using a broken piston ring
Next, insert all piston rings one by one into the cylinders from the bottom of the crankcase. Insert the rings into the cylinders with the back of the piston in accordance with Figure 93. In this case, they sit directly in the cylinder bore. It should be taken into account that the wear criteria for 1.6 l and 2.0 l engines are different, i.e. the specified immersion depth must be observed. To measure the thermal clearance of the piston ring lock, insert a feeler gauge into the ring lock, as shown in Figure 94. If the size exceeds the data given in the table of sizes and adjustments, replace the piston rings. It should be taken into account that the thermal clearance is not the same for all rings and for all engines.
Fig. 93. Measuring the thermal clearance of the piston ring lock in the cylinder. Extend the inverted piston to a depth of (between the arrows) 110 mm on a 2.0 l engine or 87 mm on a 1.6 l engine.
Fig. 94. Measuring the thermal clearance of the piston ring lock
Check for wear or scoring on the piston pins. If only one connecting rod is rejected, the entire set should be replaced. The connecting rod bearing nuts must be replaced. Also check the bending and twisting of the connecting rods on a special installation (see fig. 95), which must be minimal, i.e. over a length of 100 mm they may be bent by no more than 0.05 mm. Internal twisting is permissible at 0.15 mm per 100 mm on a 2.0 l engine and 0.05 mm per 100 mm on a 1.6 l engine. The connecting rod head bushings are not subject to replacement.
Fig. 95. Connecting rods are checked for bending and twisting on a straightening machine. The bending test is shown here. When checking twisting, a feeler gauge is set in the place indicated by the arrows.