3.10. Pistons and rods

Remove a head of the block of cylinders and the oil pallet.
Turn a bent shaft and install pistons of the first cylinder in the provision of the lower dead point (LDP).
If in the top part of the cylinder the fillet was formed, then it needs to be removed development or a shaber, without having damaged a cylinder wall. Formation of a fillet indicates the increased wear of the cylinder.
Turn off bolts of fastening of a conrod cover of the first cylinder. Uncover and take out the lower connecting rod. If the insert is established again, paste it an adhesive tape to uncovered.
The handle of the hammer push the piston in the cylinder and get it through the top part of the block of cylinders. Remove the top insert of the conrod bearing and paste it an adhesive tape to the removed rod.
Put a cover on a rod and fix by bolts to keep a former assembly order of details.
Having repeated the specified operations, remove rods with pistons in other cylinders.
Before check of pistons with rods remove piston rings from pistons and carefully clear pistons.
For removal of piston rings from pistons unclench a ring and insert under it evenly on a circle two or three old edges of the probe and on them shift a ring from the piston. Be careful, do not scratch the piston the ends of a ring. Rings very fragile can also burst if to unclench them very strongly. Handle with care with sharp working edges of piston rings not to be cut. You hold each set of rings together with pistons for repeated installation them on the places.
Clear all traces of a deposit from the top part of the piston.
Remove a deposit from flutes under piston rings, using an old piston ring.
After removal of a raid clear the piston with a rod the corresponding solvent and wipe dry.
Carefully examine each piston on existence of cracks around a skirt and openings under a piston finger.
Check wear on a skirt of the piston, an opening in a piston head, and also existence of a progar in the top part of the piston.
Traces of pointed corrosion on the piston specify that cooling liquid got to the combustion chamber. It is necessary to find out the reason of hit of liquid in the combustion chamber and to eliminate it.
Define a piston gap in the cylinder, equal to a half of a difference of diameters of the cylinder and piston.
Check each rod for wear, existence of cracks and distortion of a form.
Rods usually do not demand replacement if did not jam the engine.
At installation it is necessary to execute the following.

Fig. 3.1-74. Piston and rod: 1 – lock ring; 2 – piston finger; 3 – piston; 4 – piston rings; 5 – rod; 6 – conrod cover; 7 – a bolt, 30 N · + to tighten m on a corner 90 °; 8 – connecting rods


Before installation of a piston finger of 2 (fig. 3.1-74) it is necessary to heat the piston 3 to temperature of 60 °C.
Note assembly position of the piston and number of the cylinder in which it is installed.
The arrow on the bottom of the piston indicates a belt pulley.
Before installation of the piston in the cylinder, piston rings it is necessary to squeeze a coupling tape collar.
Measure diameter of the piston.
Locks of piston rings settle down at an angle 120 °.
The tag of "TOP" on a piston ring has to be directed to the piston bottom.
Measure a gap in the lock of a piston ring.
Check a gap between a piston ring and a flute of the piston.
Identification tags And which have to settle down on the one hand are applied on a rod and a cover of a rod.
On a rod and a cover of a rod the identification inflows In defining the assembly provision of a rod are executed. In cylinders 1-3 identification inflows have to settle down from a belt pulley, and on cylinders 4-6 – from a flywheel.
At installation it is necessary to use new bolts 7.
Before a vvertyvaniye of bolts the carving and a basic surface of heads of bolts need to be oiled.
At installation it is necessary to observe the correct assembly provision of a connecting rod.

Check of a gap in the lock of a piston ring

Fig. 3.1-75. Use of the probe for measurement of a gap in the lock of a piston ring



Insert a ring into the corresponding cylinder and push the piston bottom on depth of 15 mm to exclude a ring distortion at measurement then get the piston. Measure a gap by the probe (fig. 3.1-75). If the gap exceeds norm, then replace rings and repeat the procedure.
If the gap is too small (that is improbable), it is the best of all to pick up new rings with a standard gap in the lock. Otherwise because of a smykaniye of rings during the operation of the engine there will be serious breakages. As a last resort the gap can be increased, having accurately filed ring lock end faces a thin file. For this purpose clamp a file in a vice with soft sponges, get a ring so that end faces of the lock appeared on both parties of a file, and, slowly moving a ring, remove excessive material. Keep in mind that the ring very fragile and can easily break.

Check of a gap between piston rings and flutes of pistons

Fig. 3.1-76. Use of the probe for measurement of a gap between a piston ring and a wall of a flute of the piston



Check a gap between a piston ring and a wall of a flute of the piston. For this purpose insert a ring from the outer side into the corresponding flute and measure by the probe a gap between the top surface of a ring and a wall of a flute (fig. 3.1-76). If at installation of a new ring the gap exceeds norm, then replace the piston.

Measurement of diameter of the piston

Fig. 3.1-77. Use of a micrometer for measurement of diameter of the piston



Measure by a micrometer diameter of the piston in the plane, a perpendicular axis of a piston finger, at distance of 10 mm from bottom edge of a skirt of the piston (fig. 3.1-77). The measured value has to differ from nominal rate no more than on 0,04 mm. If wear of the piston exceeds maximum permissible, then the piston is subject to replacement.

Measurement of diameter of the cylinder
Diameter of the cylinder is measured in three planes in the cross and longitudinal directions (fig. 3.1-78). The gap between the piston and the cylinder is defined as a difference of the measured diameters of the cylinder and piston.

Fig. 3.1-78. Places of measurement of diameter of the cylinder



The deviation of diameter of the cylinder from nominal rate should not exceed 0,08 mm.

Pistons
Using a waterproof marker, apply identification tags on the bottoms of pistons. The arrow on the bottom of the piston indicates a belt pulley.

Rod
Rods do not demand replacement, except for cases of jamming of the engine or other serious breakages. Check a condition of rods visually, hand over the deformed rods on car repair shop for check and repair by the skilled expert.
Replacement of a rod is made only together with a conrod cover.
At removal connecting rods surely establish on former places.
Before removal check existence of identification tags on a rod and a cover of a rod. Apply on covers of a rod of number of the corresponding cylinders in which they are established.
The radial gap of a rod is checked as well as a radial gap in radical bearings of a bent shaft, with application of a plastic core of Plastigage.

Prevention
After unscrewing of bolts of fastening of an inlet collector all bolts of fastening of a head of the block of cylinders should be tightened repeatedly a dovorachivaniye on a corner 90 °.

Fig. 3.1-79. Head of the block of cylinders: 1 – head of the block of cylinders; 2 – laying; 3 – inlet collector; 4 – bolt, 20 N · m; 5 – bolts of fastening of a head of the block of cylinders; 6 – maslootrazhatel; 7 – laying of a cover of a head of the block of cylinders; 8 – cover of a head of the block of cylinders; 9 – bolt, 10 N · m; 10 – valve of restriction of pressure of 2,7 bars, 25 N · m; 11 – bolt, 10 N · m; 12 – casing; 13 – bolt, 22 N · m; 14 – conic washer; 15 – rotor; 16 – laying of a head of the block of cylinders