Replacing the piston rings of the YaMZ diesel engine of the MAZ car

Piston rings during engine repair are replaced in the following cases:

  • - when the engine has run more than 150 thousand km;
  • - fully or partially worn grooves on the working surface of the second and third compression rings;
  • - the presence of burrs on the outer cylindrical surface of the rings.

To replace the piston rings, first dismantle the piston with the connecting rod with the cylinder head and sump removed.

Engines are equipped with oil-cooled pistons.

When dismantling the piston group on these engines, first remove the piston cooling nozzles in order to avoid their breakdowns, to make the piston easier to remove, clean the carbon deposits from the upper belt of the sleeve.

Unscrew the connecting rod cover bolts, remove the cover and remove the piston assembly with the connecting rod through the cylinder.

To disconnect the connecting rod from the piston, remove the piston pin circlips, heat the piston in an oil bath to 80 ° C and remove the piston pin.

Piston Ring Pliers

To remove the piston rings, put the pliers (Fig. 1) on the ring, insert the jaws of 2 pliers into the lock of the ring and, squeezing the handles of 3 pliers to the stop

Removing and putting piston rings on piston

Carefully slide the ring out of the groove and remove it from the piston (fig. 2).

Install the piston rings in reverse order.

Carefully clean the piston from carbon deposits, protecting it from damage (especially the end surfaces of the grooves for the piston rings).

Before assembling, thoroughly rinse all parts and blow out the oil channels with compressed air.

Assemble the piston with a finger by lightly pressing the hand, while it is necessary to generously lubricate the hole in the piston and the finger with engine oil. It is not allowed to press the finger into the piston.

Drift for installing piston in cylinder liner

In order to install the piston assembly with piston rings and connecting rod into the cylinder liner, pre-compress the rings by sinking them into the piston grooves.

To compress the rings, use a mandrel (Fig. 3) with a conical inner surface and a collar that allows the mandrel to be correctly centered on the cylinder liner.

Having installed the piston in the mandrel, push it into the cylinder liner.

When assembling the piston with the connecting rod and installing them on the engine, fulfill the following requirements:

  • 1. The piston and sleeve must be of the same size groups.
  • 2. Install the compression rings with the stamp “up” to the piston bottom.
  • 3. Separate the locks of adjacent piston rings in opposite directions in the plane of the piston pin.
  • 4. Install the piston so that the offset combustion chamber in the piston points into the engine, towards the fuel pump.

Pistons with a central combustion chamber are used on YaMZ-2Z6NE2, BE2 engines with individual cylinder heads.

Install the piston in the sleeve so that so that the arrow on the piston points to the engine camber, towards the fuel pump.

In this case, the grooves on the piston bottom for the valves will be shifted relative to the center of the cylinder towards the exhaust manifolds.

  • 5. The mating marks on the connecting rod and the cap must be the same.
  • 6. Dirt, burrs and nicks on the splines of the connecting rod and cap are not allowed.
  • 7. Lubricate the threads and bearing ends of the heads, bolts for fastening the connecting rod caps with engine oil and tighten in two stages, starting with a long bolt, first with a torque of 100 Nm (10 kgcm), finally with a torque of 200 - 220 Nm (20 - 22 kgcm).