3.4.35. Pistons and rods Replacement of a piston finger Replacement of conrod bearings Caps of channels of the block of cylinders

The conrod and piston group is recommended to be changed on the dismantled engine at full dismantling. If works are performed on the car, then it is necessary to remove a head of cylinders and the pallet.

Removal of a fillet in the top part of the cylinder

Order of installation of rings on the diesel

1. Installation order
2. Marking

Orientation of the piston on the diesel

1. Marking
2. Stamp of dimensional group
3. An arrow (it is directed forward)

Orientation of the piston on V6 engines

1. Marking
2. An arrow (it is directed forward)

1. The piston with a rod is pushed out through the top part of the block of cylinders after an otvorachivaniye of bolts of conrod covers and removal of a fillet in the top part of the cylinder. Rods are marked according to number of the cylinder. Covers of rods before removal should be numbered. Remove rings special adaptation.
2. Clear pistons, having removed a deposit.


1. Check ovality and conicity of cylinders. For this purpose check diameter of cylinders, having measured it in the longitudinal and cross directions concerning an engine axis, in three places – directly under a fillet, in the lower part of the cylinder and in the middle.
2. If conicity and ovality within norm, then cylinders to an otkhonninguyta. Otherwise cylinders should be chiseled and replaced pistons and rings repair (these procedures are performed in car service).

3. Check deformation of the demountable plane of the block of cylinders. If the deviation from the plane is more than 0,1 mm, then the block to a proshlifuyta.
4. Check a condition of the piston. Existence of cracks about a skirt, and also deep noticeable scratches and рисок on a side surface is not allowed.
5. Measure diameter of the piston in the direction perpendicular axes of a piston finger at the level of a skirt. Define a gap between the piston and the cylinder. If the gap is higher than norm, then replace the piston. If when replacing the piston the gap does not meet standard, then chisel cylinders and replace pistons repair.

6. Check a gap between compression rings and a flute in the piston. If the gap is a little higher than norm, then it is necessary to replace rings.

7. Check gaps in joints of piston rings, having pushed a ring the piston (1 piston, 2 – a ring, 3 – a gap). In 15 mm from bottom edge of the cylinder gaps have to meet standard.
8. Check a condition of rods external survey. Existence of deformations, a curvature of an arc bed under an insert in the lower part and not parallelism of hairpins of fastening of a conrod cover are not allowed. The notable side play of a piston finger in a rod should not be (the finger is pressed in a rod). The damaged rod is prepared in car service or changes.

Arrangement of joints of piston rings

1. The top compression
2. Top disk of an oil scraper ring
3. Lower compression and dilator of an oil scraper ring
4. To a forward part of the engine
5. Lower disk of an oil scraper ring

1. New rings have to correspond to dimensional group of the piston. All gaps in rings have to be checked and meet standard.

2. Establish rings as it should be: an oil scraper ring, lower compression, top compression (this ring is established only by means of a dilator). The tag on a ring has to be turned up. 

3. Sections of the top and lower compression rings differ (1 – marking of N and T, 2 – the rounded profile, 3 – a conical profile).
4. Place joints of piston rings.

5. Grease the cylinder, press out rings adaptation, correctly orient and enter into the cylinder the piston assembled with rings and a rod and the top insert. Establish the lower insert in a cover, fix a cover by nuts. Repeat the procedure for other rods, turning the crankshaft. Tighten nuts with the set moment in 2–3 stages.
6. Establish all removed details (if repair was carried out without removal of the engine).