Pic. 2.267. Piston and connecting rod
Disassembly of the connecting rod cap
Loosen the connecting rod cap bolts, then remove the connecting rod cap and lower connecting rod bearing.
Push the piston and connecting rod assembly out of the cylinder block towards the cylinder head gasket surface.
Attention! Position the removed parts (connecting rods, connecting rod caps, connecting rod bearing shells) in order of their respective cylinder numbers to ensure correct reassembly.
Disassembly and assembly of the piston and connecting rod assembly (removal and installation of the piston pin)
Pic. 2.268. Disassembly of the piston-rod assembly
With special tools (09234-33001 and 09234-33002) disassemble and assemble the piston and connecting rod assembly (pic. 2.268).
The piston pin is pressed into the upper head of the connecting rod, and the piston slides over it.
A set of special tools consists of a base with a stand and inserts, guides, adapters, a push rod for removal and a push rod for installation. When removing or installing a piston pin, the piston is held on the base of the tool. Piston guides make it easier to position the piston pin when removing and installing it when the connecting rod rests on the pedestal inserts.
Pic. 2.269. Removing a finger with a press
To remove the piston pin, place the piston on the base and position the connecting rod on the pedestal insert. Insert push rod (for removal) through the arc of the top of the base into the piston pin and remove the pin with a press (pic. 2.269).
When installing a new pin, you must install the appropriate stand insert to support the crank.
Position the top end of the connecting rod inside the piston. On one side of the piston, insert the appropriate guide through the piston and connecting rod, then slightly push the guide back by hand so that it is held by the piston. On the other side of the piston, insert the piston pin and place the piston and connecting rod together on the base of the tool with the pin guide on the bottom.
Pic. 2.270. Connecting rod centering guide
Note. The guide is needed to center the connecting rod relative to the piston bosses. If assembled correctly, the finger guide will be exactly centered on the arc hole on the top of the base and touching the stand insert. If the wrong size pin guide is used, the piston (and connecting rod) and the piston pin will not be in the same axis with the hole in the base (pic. 2.270).
Insert push rod (for installation) through the hole in the arc of the upper part of the base until it stops against the adapter on the piston pin and, using a hydraulic press, insert the finger into the piston and the upper head of the connecting rod. Continue pressing until the pin guide falls from the bottom of the base and the push rod rests against the arc of the top of the base.
Attention! Do not exceed the force of 12,500±5,000 N when pressing in the piston pin at the moment when the push rod rests against the arc of the upper part of the base.
Checking the piston and piston pin
Check each piston for scratches, nicks, wear and other defects. Replace piston if defective.
Check each piston ring for breaks, damage or significant wear. Replace defective rings. If a piston needs to be replaced, its piston rings must be replaced at the same time.
Check that the piston pin fits into the piston bosses. Replace piston and piston pin as a set if defective. At room temperature, the piston pin should easily, without sticking, enter the piston bosses by hand.
Checking piston rings
Pic. 2.271. Checking the End Gap of the Compression Ring
Measure the clearance between the compression ring and the piston groove (pic. 2.271).
If the measured clearance exceeds the limit, install a new piston ring and re-measure the clearance. If the measured clearance again exceeds the limit value, replace the piston and rings as an assembly. If the measured clearance is less than the limit value, replace only the piston rings.
The clearance values between the piston ring and the piston groove are shown below.
Rated value:
- compression ring No. 1 - 0.04–0.08 mm;
- compression ring No. 2 - 0.03–0.07 mm.
Maximum allowable value:
- compression ring No. 1 - 0.1 mm;
- compression ring No. 2 - 0.1 mm.
For measurement of a backlash in the lock of a piston ring establish a piston ring in an opening of the cylinder.
Position the ring at right angles to the generatrix of the cylinder wall, carefully moving it down with the piston. Measure the gap in the ring lock with a flat feeler gauge. If the measured clearance exceeds the limit, replace the piston ring.
Measure the gap in the ring lock with a flat feeler gauge.
If the measured clearance exceeds the limit, replace the piston ring.
Piston ring gap values are shown below.
Rated value:
- compression ring No. 1 - 0.20–0.35 mm;
- compression ring No. 2 - 0.37–0.52 mm;
- oil scraper ring - 0.2–0.7 mm.
Maximum allowable value:
- compression rings No. 1 and No. 2 - 0.8 mm;
- oil scraper ring - 1.0 mm.
When replacing piston rings without boring the cylinders to the repair size, check the clearance in the ring lock at a point located at the bottom of the cylinder (zone of least wear).
When installing the connecting rod cap, make sure that the cylinder number marks (made during disassembly) matched on the connecting rod and the connecting rod cap. When installing a new connecting rod, make sure that the retaining grooves of the bushings in the connecting rod cap and connecting rod are on the same side.
Replace the connecting rod if there is damage to the end surface of the upper or lower heads. If bending or twisting of the connecting rod is present, or the surface of the piston pin bore in the upper end of the connecting rod is significantly worn, replace the connecting rod.
Note. An identification mark is applied to the upper surface of the ring next to the lock.
Checking the connecting rods
When installing the connecting rod cap, make sure that the cylinder number marks (made during disassembly) matched on the connecting rod and the connecting rod cap. When installing a new connecting rod, make sure that the retaining grooves of the bushings in the connecting rod cap and connecting rod are on the same side.
Replace the connecting rod if there is damage to the end surface of the upper or lower heads. If bending or twisting of the connecting rod is present, or the surface of the piston pin bore in the upper end of the connecting rod is significantly worn, replace the connecting rod.
Assembly
Pic. 2.272. Installing the oil ring expander
Install the oil ring expander (pic. 2.272).
Pic. 2.273. Scheme of installation of the upper scraper of the oil scraper ring
Install the top oil ring scraper. To do this, first install one end of the scraper between the expander and the piston groove, then, holding the end of the scraper, press the scraper with your finger to bring it into the groove, as shown in Figure 2.273.
Attention! Do not use a piston ring expander when installing oil scraper scrapers.
Pic. 2.274. Installation of the bottom scraper of an oil scraper ring
Install the lower oil scraper according to the previous procedure (pic. 2.274).
Apply engine oil to the piston and piston ring grooves all around.
Using a piston ring expander, install compression ring #2.
Pic. 2.275. Scheme of installation of a compression ring No. 1
Install compression ring #1 (pic. 2.275).
Pic. 2.276. Scheme of locks of compression rings
Position the locks of the rings as far apart as possible. Make sure that the lock of any ring is not on the axis of the piston pin or a direction perpendicular to this axis (pic. 2.276). Before installing the piston and connecting rod in the cylinder, use a mandrel to compress the piston rings.
Install the upper main bearing shells into the block.
Pic. 2.277. Installing the lower main bearing shells
Install the lower bearing shells into the main bearing caps (pic. 2.277).
Attention! The upper main bearing shells have an oil distribution groove.
Pic. 2.278. Installing thrust bearing half rings
Install the thrust bearing halves into the #3 main bearing cap with the oil grooves facing out (pic. 2.278).
When installing the piston, make sure that the mark «before» on the piston and mark «before» on the connecting rod pointing towards the front of the engine (to the timing belt).
When installing the connecting rod cap, the cylinder number on the cap and connecting rod must be on the same side.
When installing a new connecting rod, make sure that the bearing tabs on the connecting rod and connecting rod cap are on the same side.
The connecting rod cap bolts are tightened using the angular method.
1. Apply oil to the threads of the fastening nuts and the connecting rod nuts and bolts.
2. Tighten the connecting rod cap bolts to the rated torque and tighten to the specified angle.
Tightening torque for connecting rod cap nuts: 16–20 N·m + 90–94°.
Attention! Do not re-install old connecting rod cap bolts.
Attention! When using a new bolt, tighten it no more than three times.
Pic. 2.279. Checking the side clearance between the lower head of the connecting rod and the web of the crankshaft
Check the backlash between the bottom head of the connecting rod and the web of the crankshaft (pic. 2.279).
Lateral clearance of the lower head of the connecting rod:
- Nominal value - 0.10–0.25 mm;
- The maximum allowable value is 0.40 mm.