4.3.18. Check of a condition of components of conrod and piston group


1. Previously conrod and piston assemblies have to be carefully cleared. Rings need to be removed from pistons.

Piston rings are subject to replacement without fail.

2. By means of special adaptation remove rings from pistons, - try not to damage walls of the last incidentally.
3. Scratch out traces of coal deposits from the bottoms of pistons. After removal of the main layer of deposits smooth out a surface manually a wire brush or a piece of a fine-grained emery paper.

Do not use for cleaning made of soft material and pistons easily subject to an erosion wire nozzles to the electric drill at all!

4. By means of special adaptation clean flutes under installation of rings on pistons. It is alternatively possible to use a fragment of an old piston ring for this purpose, however be careful, - do not scratch a bottom and walls of a flute and do not cut fingers.

5. Having removed the main deposits, wash out conrod assemblies by solvent and carefully dry them, whenever possible with use of compressed air. Check passability of maslovozvratny openings in back walls of flutes under installation of piston rings, and also oil openings in the lower heads of rods.

When using compressed air do not forget to put on goggles!

6. If walls of pistons and a mirror of cylinders are not damaged and excessively are not worn-out, and the block of the engine was not pierced and not replaced, need for replacement of pistons also disappears. Normal wear of pistons is shown in the form of vertical traces of development on a persistent surface and a small weak point of landing of the top compression ring in the flute. Do not forget that replacement of piston rings is made without fail, regardless of their state.
7. Attentively examine each of pistons on existence of cracks in a skirt, around ledges under installation of piston fingers and around an arrangement of rings.
8. Check persistent surfaces of a skirt of the piston for existence of scratches, the bottom - on existence of through openings and progar on edge. Presence of scratches on a skirt can be regarded as a sign of long overheats of the engine, or too early ignition of air-fuel mix, - check serviceability of functioning of the cooling system. Progara at the edges of the bottom are the certificate of a detonation. Anyway, the cause of the revealed violation has to be removed in order to avoid a recurrence. Also leak of the soaked-up air, the wrong configuration of air-fuel mix, violation of installation of a corner of an advancing of ignition, the wrong functioning of systems of ignition and EGR can act as the possible reasons of education listed defects.
9. Pointed corrosion of pistons in the form of cavities speaks about hit in combustion chambers and/or a case of the engine of cooling liquid. Besides, take care that the cause of internal leaks was removed.

10. Estimate the size of a side gap of landing of piston rings in the flutes for what enclose a new ring outside in the flute on the piston and the probe of lezviyny type measure the remaining gap. Repeat measurement in two-three points on flute perimeter. You watch to mixing compression rings, - top differs from the second. If the size of a gap exceeds admissible value (see Specifications), pistons are subject to replacement.

11. Define a landing gap of pistons in the cylinders for what measure diameters of the last (see the Section Check of a Condition of the Block) and subtract from them diameters of the corresponding pistons. Measurement of diameter of the piston is performed on a persistent surface at an angle 90 ° to an axis of a piston finger and on the set removal from the bottom. If the landing gap of the piston in the cylinder exceeds admissible value (see Specifications), the block should be given to a pro-point with a selection of new pistons and piston rings of repair diameter.

12. Estimate correctness of landing of pistons on rods, having tried to rotate components in opposite directions. Existence of a little noticeable side play speaks about excessive wear of a joint. For correction of a situation it is necessary to deliver conrod and piston assemblies in a workshop of car service where necessary recovery repair and replacement of fingers will be made.
13. Implementation of the procedure of removal of pistons from rods (in case of such need) has also to be entrusted to specialists of car service. In parallel, rods can be checked for existence of signs of a bend, twisting and other deformations with use of the special diagnostic equipment.

Needlessly it is not necessary to remove pistons from rods.

14. Check rods for existence of cracks and other mechanical damages. Temporarily uncover the lower heads, take inserts of old bearings, wipe beds in covers and heads and check them for existence of agnails, zadir and roughnesses. Having finished check, enclose inserts into place, establish covers on the lower heads of rods, and by hand tighten fixing bolts.

If the engine is under repair for the purpose of elimination of knock of fingers, replace conrod assemblies.