Attention! When completely disassembling the engine, the piston rings must be replaced, regardless of their condition.
2. Remove carbon deposits from piston ring grooves (see photo).
3. Wash the pistons and connecting rods with solvent, thoroughly clean the oil drainage holes in the piston grooves and the hole in the connecting rod.
4. If there are no significant signs of wear and if the cylinders do not require boring, then the pistons should not be replaced. Normal wear is shown as traces of uniform vertical wear on the piston friction surface and as a slight weakening of the upper compression ring fit. However, replacement of piston rings is mandatory.
5. Carefully check for cracks on the piston skirt, piston pin bosses and piston ring seats.
6. If there are chips and scuffs on the piston, this indicates frequent overheating of the engine. In this case, a thorough check of the lubrication and cooling systems is required. Burning of the piston bottom indicates that the engine is operating with an incorrect ignition timing setting.
7. The cause of piston bottom burning at the edges is usually abnormal combustion (detonation). If the above defects are detected, their cause must be determined and eliminated, (as a rule, the cause is air suction in the manifold through a leaky gasket, a malfunction of the devices for preparing the combustible mixture or the recirculation system).
8. Piston corrosion in the form of small pits (pitting) indicates penetration into the combustion chamber (and also in the crankshaft housing) Coolant.
9. Measure the gap between the groove and the new ring (see photo). If the clearance exceeds the established limit, the piston should be replaced.
10. Check the clearance between the piston and the cylinder by measuring the cylinder diameter (see above) and the diameter of the piston from this cylinder (see photo). If the gap, which is calculated as the difference between these diameters, exceeds the established limit, then the cylinder block must be bored, and the pistons and rings must be replaced with repair ones.
11. Check the clearance between the piston pin and the connecting rod head by rocking the piston and connecting rod in opposite directions. If the clearance is noticeable, then this connection needs to be repaired at a car service center.
12. Checking the connecting rod heads and their deformation, as well as replacing pistons and connecting rods, is only performed in a car service center.
Attention! If the pistons or connecting rods will not be changed, then disassembling this connection is not allowed.
13. Check the connecting rods for cracks and other damage. Remove the connecting rod bearing caps, take out the bearings, wipe the seating surfaces on the cap and on the connecting rod, check for cracks, scratches and burrs. After checking, assemble the connecting rod, install the bearings in place, tighten the nuts by hand.