The inspection and fault diagnosis of the connecting rod and piston assembly were covered in the article “Repair of the connecting rod and piston assembly”.
Let us briefly go over the main features once again:
Before fitting the liners into the cylinder block, if required, the block is thoroughly washed and dried.
When replacing liners, the new liners are inserted into the cylinder block so that the letter designating the liner group is located in the transverse plane.
The liner must enter the block completely freely.
The liner fitted with the copper gasket in the block must protrude above the block surface by 0.02–0.1 mm.
The difference in liner protrusion across the cylinders must be no more than 0.055 mm (this is ensured by selecting liners by length or by settling them with deformation of the copper gasket).
Before fitting the liner, the place on which the liner rests in the block must be coated with sealant (previously oil paint was used during assembly).
After inserting the liner into the cylinder block, we press the liners home with light taps.
After fitting the liners, they must be fixed using suitable bushes, washers and nuts.
The fixing is needed so that when the block is turned over and the pistons with rings are inserted, the liners do not come out of the block.
Regarding the fault diagnosis of the block, the relevant article was covered.
We proceed to the assembly of the connecting rod and piston assembly.
Two designations are stamped on the piston crown.
A letter is applied to the block with paint. The piston is selected for the cylinder by this letter.
Of course, if the cylinder-piston group has been changed, this marking is no longer taken into account.
On the piston crown, a Roman numeral indicates the piston group.
On the piston pins, the group number is indicated with paint on the inner surface or on the ends. It must of course coincide with the piston group.
On the connecting rod, the group number is also designated with paint.
It must either coincide with or be adjacent to the pin group.
The piston pin, lubricated with engine oil, must move in the connecting rod small end with slight effort, but must not fall out of it.
We heat the piston to a temperature of about 80 °C (possible in a water bath) and press in the piston pin.
The pin can be pressed in with a copper or ordinary hammer, through a drift of soft metal, holding the piston suspended.
After assembly, the lug on the connecting rod big end must be on the same side as the inscription “Перед” (Front) on the piston.
The orientation lug of the connecting rod of the ZMZ-402 engine is located not on the connecting rod shank but on its cap.
We fit the circlips into the piston.
We check the piston rings.
The compression rings fitted into the cylinder to a depth of 20–30 mm must have an end gap of 0.3–0.6 mm, the oil scraper ring — 0.5–1 mm.
We fit the rings onto the piston.
We spread the expander gap of the oil scraper ring, fit it onto the piston into the lower groove and close the gap.
We fit the lower compression ring with the inscription “ВЕРХ” (TOP) towards the piston crown.
Lastly, we fit the upper compression ring.
We turn the rings so that the gaps of the upper compression rings are on opposite sides of the piston, and the gap of the oil scraper ring is at 90° to the gaps of the compression rings.
When replacing worn or defective liners with new and repaired ones, they must be inserted into the block so that the mark on the lower centring part of the liner, indicating its group, is located in the transverse plane of the block.
In other cases, before removing the liners from the block, they must be marked with serial numbers, and their position in the block must be marked, so that during assembly they are refitted in their previous position.
In the case of replacing pistons, liners, piston pins or connecting rods, the selection of mating pairs must be carried out at a temperature of the parts of 20±3 °C (see the table of size groups below).
When fitting new rings to the piston but retaining the previous liners, the protruding collar in the upper part of the liner must be removed on a machine or with a scraper.
For lightly worn cylinder liners without boring, a set of tinned compression rings and steel oil scraper rings is provided.
We install the engine block on the stand in an inverted position.
We insert into the main bearing seats the shells with a groove and an oil supply hole.
We insert two thrust half-rings without lugs on both sides of the centre seat.
We turn them with the transverse grooves towards the crankshaft webs.
We insert two thrust half-rings without lugs on both sides of the centre seat.
We lubricate the shells and the crankshaft main journals with engine oil.
We fit a new packing — as described in the article “Crankshaft repair”.
We insert the packing into the packing retainer and fit the rubber flags into the packing retainer.
We compress the packing, as described in the article “Crankshaft repair”.
We lay the crankshaft into the cylinder block.
We fit the shells into the main bearing caps, lubricate them with clean engine oil and lay them on the crankshaft journals.
When fitting cap 2 of the first main bearing, the lug of the rear thrust washer 1 must enter the groove of cap 2.
We fit the packing retainer.
Using an 8 mm Allen key, we screw in the two nuts securing the packing retainer.
We tighten the bolts of the main bearing caps in accordance with the tightening torques (see the torque table below).
We turn the crankshaft by hand.
The rotation must be free and uniform, without jamming, with slight effort.
The crankshaft end play must not exceed 0.36 mm.
Otherwise, we check the correctness of the assembly, dismantle and eliminate the faults.
We fit the front thrust washer 2 onto the pins 1, with the antifriction layer outwards.
We fit the spacer washer between the crankshaft sprocket and the front thrust washer.
The spacer washer is fitted with its chamfer towards the thrust washer.
We fit the crankshaft sprocket.
After pressing the crankshaft sprocket home, its end play must be checked.
The check is carried out as follows: place a screwdriver (a pry bar, a hammer handle, etc.) between the first crank of the shaft and the front wall of the block and, using it as a lever, push the shaft towards the rear end of the engine.
Using a feeler gauge, determine the clearance between the end face of the rear thrust bearing washer and the plane of the collar of the first main journal.
The clearance must be within 0.125–0.325 mm.
We insert new shells into the connecting rod and its cap.
We lubricate the piston rings, shells, cylinder walls and big-end journals with engine oil.
We fit the ring compressor tool and, tapping in a circle with the wooden handle of a hammer, compress the rings.
We orient the piston correctly with the inscription “Перед” (Front) towards the front part of the block and insert it into the cylinder according to the number order.
Tapping with the wooden handle of a hammer on the piston crown, we sink it into the cylinder.
On the other side we check its correct position relative to the crankshaft journal.
We fit the connecting rod caps.
Using a 15 mm socket, we screw in the connecting rod cap nuts to a torque of 6.8–7.5 kgf·m. We use a torque wrench for tightening.
We fit the camshaft.
Before fitting the camshaft, lubricate with engine oil the camshaft journals and cams, the tappets and the tappet rods.
When fitting the camshaft, align the mark on its plastic sprocket with the “0” mark on the crankshaft sprocket.
We fit the camshaft.
Using a 12 mm socket, through the hole in the sprocket, we screw in the bolts securing the thrust flange.
We fit the oil deflector washer onto the end of the crankshaft.
We insert the pulley hub key into the crankshaft seat.
We fit the timing sprocket cover.
For the crankshaft front oil seal to seat correctly, it is best to centre the cover together with the pulley hub.
Before seating the pulley hub, lubricate the working edge of the oil seal with engine oil.
Using a 13 mm spanner, we screw in the eight cover mounting nuts.
The tappets are selected according to the dimensions of the holes in the block and are divided into two groups (see the table of tappet size groups).
The crankshaft, flywheel and clutch are balanced as an assembly; therefore, when replacing one of these parts, dynamic balancing must be carried out by drilling metal from the heavy side of the flywheel.
Balancing of the crankshaft, flywheel and clutch as an assembly must not be started if the initial imbalance exceeds 200 g·cm.
In this case, the assembly must be dismantled and the balance of each part checked separately.
After pressing the crankshaft sprocket home, its end play must be checked.
We fit the oil pump.
We engage and screw in with a 13 mm spanner the two nuts securing the oil pump.
We fit a new sump gasket. We coat the sump gasket with sealant on both sides.
We fit the sump and tighten the sump nuts in a crosswise sequence.
A ball bearing 80203 АС9 with two protective washers is pressed into the rear end of the crankshaft.
It is permitted to use bearing 60203А with one protective washer; in this case, 20 g of Litol-24 grease must be placed in the bearing cavity.
Bolt to the flywheel the clutch pressure plate as an assembly with the housing, having previously centred the driven plate with a drift (the gearbox input shaft may be used) through the hole in the bearing at the rear end of the crankshaft.
The 0 marks stamped on the pressure plate housing and on the flywheel near one of the holes for the housing mounting bolts must be aligned.
Coat the joints of the lower flange of the cylinder block with the timing sprocket cover and the packing retainer with “Elastosil 137-83” sealant adhesive or УН-25 paste.
Tightening torques of the threaded joints of the ZMZ-402 engine
Joint designation / Tightening torques, kgf·m:
- Spark plugs: 3.0–3.5
- Cylinder head mounting nuts: 8.3–9.0
- Connecting rod bolt nuts: 6.8–7.5
- Main bearing cap mounting nuts: 10.0–11.0
- Flywheel mounting nuts: 7.6–8.3
- Clutch housing to cylinder block mounting nuts: 2.8–3.6
- Crankshaft bolt: 17–22
- Clutch pressure plate mounting bolts: 2.0–2.5
- Inlet pipe and exhaust manifold mounting nuts: 1.5–3.0
- Sump mounting nuts: 1.2–2.0
- Cylinder head mounting bolts (preliminary tightening): 4.0–6.0
- Cylinder head mounting bolts (final tightening): 13.0–14.5
- Flywheel mounting bolts: 7.2–8.0
- Clutch housing mounting bolts: 4.2–5.1
- Crankshaft bolt: 10.4–12.0
- Camshaft cap mounting bolts: 1.9–2.3
- Camshaft sprocket mounting bolts: 5.6–6.2
- Rocker cover mounting bolts: 0.5–0.8
- Inlet pipe mounting nuts, clutch housing reinforcement mounting bolts: 2.9–3.6
- Coolant pump pulley, cylinder head front cover, chain cover, thermostat housing mounting bolts: 2.2–2.7
- Seal retainer, sump mounting bolts: 1.2–1.8
- Exhaust manifold mounting nuts: 2.0–2.5
- Main bearing cap mounting nuts: 12.5–13.6
- Rocker shaft post mounting nuts: 3.5–4.0
- Oil filter mounting union: 8.0–9.0
- Oil filter: 2.0–2.5
Size groups of pistons and liners
| Group | Cylinder diameter, mm | Piston diameter, mm |
|---|---|---|
| А | nominal size 92.036 – 92.024 | nominal size 92.000 – 91.988 |
| 1st repair size 92.536 – 92.524 | 1st repair size 92.500 – 92.488 | |
| 2nd repair size 93.036 – 93.024 | 2nd repair size 93.000 – 92.988 | |
| Б | nominal size 92.048 – 92.036 | nominal size 92.012 – 92.000 |
| 1st repair size 92.548 – 92.536 | 1st repair size 92.512 – 92.500 | |
| 2nd repair size 93.048 – 93.036 | 2nd repair size 93.012 – 92.000 | |
| В | nominal size 92.060 – 92.048 | nominal size 92.024 – 92.012 |
| 1st repair size 92.560 – 92.548 | 1st repair size 92.524 – 92.512 | |
| 2nd repair size 93.060 – 93.048 | 2nd repair size 93.024 – 92.012 | |
| Г | nominal size 92.072 – 92.060 | nominal size 92.036 – 92.024 |
| 1st repair size 92.572 – 92.560 | 1st repair size 92.536 – 92.524 | |
| 2nd repair size 93.072 – 93.060 | 2nd repair size 93.036 – 92.024 | |
| Д | nominal size 92.084 – 92.072 | nominal size 92.048 – 92.036 |
| 1st repair size 92.584 – 92.572 | 1st repair size 92.548 – 92.536 | |
| 2nd repair size 93.084 – 93.072 | 2nd repair size 93.048 – 92.036 |
Size groups of pins, pistons and connecting rods
| Pin diameter, mm | Hole diameter, mm | Marking | ||
|---|---|---|---|---|
| in the connecting rod small end | in the piston boss | of pin, connecting rod and piston | of piston | |
| 25.0000–24.9975 | 25.0070–25.0045 | 25.0000–24.9975 | White | I |
| 24.9975–24.9950 | 25.0045–25.0020 | 24.9975–24.9950 | Green | II |
| 24.9950–24.9925 | 25.0020–24.9995 | 24.9950–24.9925 | Yellow | III |
| 24.9925–24.9900 | 24.9995–24.9970 | 24.9925–24.9900 | Red | IV |
Nominal and maximum permissible dimensions, fit of mating parts of the engine connecting rod and piston assembly
| Part designation | Nominal diameter, mm | Designation of mating parts | Nominal diameter, mm |
|---|---|---|---|
| Piston | 92.0 +0.048 92.0 -0.012 | Cylinder liner | 92.0 +0.084 92.0 +0.024 |
| 1st repair size 92.5 +0.048 92.5 -0.012 | 1st size 92.5 +0.084 92.5 +0.024 | ||
| 2nd repair size 93.0 +0.048 93.0 -0.012 | 2nd size 93.0 +0.084 93.0 +0.024 | ||
| Upper compression ring | 2.0 -0.012 height | Piston | 2.0 +0.075 2.0 +0.050 groove width |
| Lower compression ring | 2.0 -0.012 height | Piston | 2.0 +0.075 2.0 +0.050 groove width |
| Oil scraper ring | 0.7 -0.04 × 2 +3.5 -0.1 height of the two discs and expander | Piston | 5.0 +0.055 5.0 +0.035 |
| Piston pin | 25.0 -0.01 | Connecting rod | 25.0 +0.007 25.0 +0.003 |
| Piston pin | 25.0 -0.01 | Piston | 25.0 -0.01 |
| Connecting rod small end bush | 26.27 +0.145 26.27 +0.100 | Connecting rod | 26.25 +0.045 |
| Piston pin circlip | 2.0±0.03 thickness | Piston | 2.2 +0.12 groove width |
| Big-end bearing shells | 61.5 +0.019 – 2 (1.75 -0.005) 61.5 +0.019 – 2 (1.75 -0.012) | Crankshaft | 58.0 -0.02 |
| Connecting rod | 36.0 -0.25 36.0 -0.35 big-end width | Crankshaft | 36.0 +0.1 big-end journal width |
