2.2.18. Check of a condition of pistons / rods

Before check performance pistons/rods have to be assembled cleared and old rings are removed from pistons.

When collecting the engine always apply new rings.


  1. Carefully, using special adaptation, remove rings, pay attention to a mark (shooter) of top of a ring. Be careful not to leave on pistons of jags or dents.
  1. Remove all traces of a deposit from the piston bottom. After removal the manual wire brush or a piece of a small emery paper can be used by a scraper of bulk of a deposit. Under no circumstances do not use for removal of a deposit from pistons a wire brush in an electric drill. The piston is made of soft material and can be damaged by it.
  1. For removal of a deposit from flutes under rings use the device for cleaning of flutes. Be very careful and delete only a deposit - do not delete metal and do not leave on sidewalls of flutes of a jag or scratch.

If the device for cleaning of flutes is inaccessible, then this work can be made a fragment of an old piston ring, however, protect hands - rings can be sharp.

  1. After removal of a deposit wash out pistons / rods solvent and dry up compressed air (if it is available). Make sure that maslovozvrashchayushchy openings in side surfaces of flutes under rings pure.
  2. If walls of cylinders and pistons are not damaged and have no excessive wear and if the block of cylinders was not exposed to grinding, then new pistons will not be required. Normal wear of the piston is shown in the form of uniform wear of persistent surfaces (at an angle 90 ° to an opening under a finger) and in the form of an insignificant side play in a flute of the top ring. However, at restoration of the engine it is necessary to establish new rings always.
  3. Attentively examine in search of cracks each piston around a skirt, on lugs of a finger and in flutes under rings.
  4. Examine persistent surfaces of a skirt in search of furrows and wear, the bottom - on existence of openings and edge of the bottom on existence of the burned sites. If the skirt has furrows or traces of attrition, then, perhaps, the engine was exposed to an overheat and / or abnormal extent of compression which causes emergence of the increased working temperatures takes place.
  5. It is necessary to check the cooling system and the lubrication system carefully. The opening in the bottom of the piston demonstrates that abnormal extent of compression (early ignition) took place. Obgoraniye traces on the edge of the bottom usually are a sign of explosive combustion (detonation). If there is any of these problems, then it is necessary to remove the cause, otherwise malfunction happens again. Malfunction can represent leaks in the inlet pipeline, wrong fuel / air mix or the wrong installation of ignition. On later models with the difficult control systems of release which are turning on catalytic converters, the problem can come from the EGR system (recirculation of the fulfilled gases) if it is applied.
  6. The corrosion of the piston having an appearance of small deepenings demonstrates penetration into the combustion chamber and/or a case of a cooler, in the same way, it is necessary to remove the cause, otherwise the problem will arise again.
  1. Measure a side gap of a piston ring, having established a new piston ring in a flute and having inserted between it and a side surface of a flute, the probe.
  1. Check a gap in three or four places around each flute. Make sure that you check the corresponding ring - rings different. If the gap is more admissible, the piston needs to be replaced.
  1. Check a piston gap in the cylinder by subtraction of diameter of the piston from diameter of the cylinder. Make sure that pistons and cylinders approach to each other. Measure diameter of the piston at the level of a skirt along a finger and at an angle 90 ° to it.
  1. Any distinctions in these measurements demonstrate ovality existence. Subtract diameter of the piston from diameter of the cylinder and receive gap size. If the gap is more admissible, the block should be ground and installed new pistons and rings.
  2. Check a side play between the piston and a rod, turning them in opposite directions. Any noticeable side play testifies to excessive wear which needs to be eliminated. The piston/rod assembled needs to be sent for check to a workshop. After repair check rods for a bend and twisting as the majority of mechanical workshops have for this purpose the special equipment.

If installation of new pistons and / or rods is not made, then do not separate pistons from rods.

  1. Check existence of cracks and other damages to rods. Temporarily uncover rod bearings, take old inserts, wipe the surfaces of bearings in a rod and in a cover, and examine them on existence of jags, dents and scratches. After check of rods establish new inserts, put covers into place and a hand tighten nuts.