3.10. Pistons and rods
Remove a head of the block of cylinders and the oil pallet.
Turn a cranked shaft and establish pistons of the first cylinder in position of the bottom dead point (НМТ).
If in the top part of the cylinder the fillet it is necessary for removing development or шабером was formed, without having damaged a cylinder wall. Fillet formation specifies in the strengthened deterioration of the cylinder.
Turn away fastening bolts шатунной covers of the first cylinder. Uncover and take out bottom шатунный the loose leaf. If the loose leaf is established again, paste its sticky tape to the removed cover.
The hammer handle push the piston in the cylinder and get it through the top part of the block of cylinders. Remove the top loose leaf шатунного the bearing and paste its sticky tape to the removed rod.
Put a cover on a rod and fix 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 from pistons piston rings and carefully clear pistons.
For removal of piston rings from pistons unclench a ring and insert under it in regular intervals on a circle two or three old edges probeа and on them shift a ring from the piston. Be cautious, do not scratch the piston the ring ends. Rings very fragile also can burst, if them to unclench very strongly. Handle with care with sharp working edges of piston rings not to be cut. Hold each set of rings together with pistons for their repeated installation 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 touch removal clear the piston with a rod corresponding solvent and wipe dry.
Carefully examine each piston on presence of cracks round a skirt and apertures under a piston finger.
Check up deterioration on a skirt of the piston, an aperture in a piston head, and also presence прогара in the top part of the piston.
Traces of dot corrosion on the piston specify that the cooling liquid got to the combustion chamber. It is necessary to find out the reason of hit of a liquid in the chamber of combustion and to eliminate it.
Define a piston backlash in the cylinder, equal to half of difference of diameters of the cylinder and the piston.
Check up each rod on deterioration, presence of cracks and form distortion.
Rods usually do not demand replacement if has not jammed the engine.
At installation it is necessary to execute the following.
Fig. 3.1–74. The piston and a rod: 1 – a lock ring; 2 – a piston finger; 3 – the piston; 4 – piston rings; 5 – a rod; 6 – шатунная a cover; 7 – a bolt, 30 Нм + to tighten on a corner 90 ; 8 – шатунные loose leaves
Before installation of a piston finger 2 (fig. 3.1–74) it is necessary to heat up the piston 3 to temperature 60 С.
Note assembly position of the piston and cylinder number in which it is established.
The arrow specifies in the piston bottom on ременный a pulley.
Before piston installation in the cylinder, piston rings it is necessary to compress a coupling tape collar.
Measure diameter of the piston.
Locks of piston rings settle down at an angle 120 .
The label TOP on a piston ring should be directed to the piston bottom.
Measure a backlash in the lock of a piston ring.
Check up a backlash between a piston ring and a piston flute.
Identification labels And which should settle down on the one hand are put on a rod and a rod cover.
On a rod and a rod cover identification inflow In, defining assembly position of a rod are executed. In cylinders 1–3 identification inflow should settle down from outside a belt pulley, and on cylinders 4–6 – from outside a flywheel.
At installation it is necessary to use new bolts 7.
Before ввертыванием bolts the carving and a basic surface of heads of bolts is necessary for oiling.
At installation it is necessary to observe correct assembly position шатунного the loose leaf.
Backlash check in the lock of a piston ring
Fig. 3.1–75. Use probeа for backlash measurement 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 warp at measurement then get the piston. Measure a backlash probeом (fig. 3.1–75). If the backlash exceeds norm replace rings and repeat procedure.
If the backlash is too small (that it is improbable), is better to pick up new rings with a standard backlash in the lock. Otherwise because of смыкания rings at engine work there will be serious breakages. As a last resort the backlash can be increased, accurately having filed end faces of the lock of a ring thin надфилем. For this purpose clamp надфиль in a vice with soft sponges, get a ring so that lock end faces have appeared on both parties надфиля, and, slowly moving a ring, remove an excessive material. Keep in mind that the ring very fragile and can easily break.
Backlash check between piston rings and flutes of pistons
Fig. 3.1–76. Use probeа for backlash measurement between a piston ring and a wall of a flute of the piston
Check up a backlash between a piston ring and a wall of a flute of the piston. For this purpose insert a ring from lateral aspect into a corresponding flute and probeом measure a backlash between the top surface of a ring and a flute wall (fig. 3.1–76). If at installation of a new ring the backlash exceeds norm 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 a plane, a perpendicular axis of a piston finger, on distance of 10 mm from a bottom edge of a skirt of the piston (fig. 3.1–77). The measured value should differ from rating value no more than on 0,04 mm. If deterioration of the piston exceeds maximum permissible the piston is subject to replacement.
Measurement of diameter of the cylinder
Diameter of the cylinder measure in three planes in cross-section and longitudinal directions (fig. 3.1–78). The backlash between the piston and the cylinder is defined as a difference of measured diameters of the cylinder and the piston.
Fig. 3.1–78. Places of measurement of diameter of the cylinder
The deviation of diameter of the cylinder from rating value should not exceed 0,08 mm.
Using a waterproof marker, put identification labels on the bottoms of pistons. The arrow specifies in the piston bottom on ременный a pulley.
Rods do not demand replacement, except for cases of jamming of the engine or other serious breakages. Check up a condition of rods visually, the deformed rods hand over on a car repair shop for check and repair by the skilled expert.
Rod replacement is spent only together with шатунной a cover.
At removal шатунные loose leaves necessarily establish on former places.
Before removal check up presence of identification labels on a rod and a rod cover. Put on covers of a rod of number of corresponding cylinders in which they are established.
The radial backlash of a rod is checked the same as also a radial backlash in radical bearings of a cranked shaft, with application of plastic core Plastigage.
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 доворачиванием on a corner 90 .
Fig. 3.1–79. A head of the block of cylinders: 1 – a head of the block of cylinders; 2 – a lining; 3 – an inlet collector; 4 – a bolt, 20 Нм; 5 – bolts of fastening of a head of the block of cylinders; 6 – маслоотражатель; 7 – a lining of a cover of a head of the block of cylinders; 8 – a cover of a head of the block of cylinders; 9 – a bolt, 10 Нм; 10 – the valve of restriction of pressure 2,7 bar, 25 Нм; 11 – a bolt, 10 Нм; 12 – a casing; 13 – a bolt, 22 Нм; 14 – a conic washer; 15 – a rotor; 16 – a lining of a head of the block of cylinders