Removing and Installing Pistons

PRECEDING WORK
Remove engine.
Remove Cylinder head.
Remove oil pan.

NOTES:
The group number of the pistons (e.g. 1) must agree with the group number of the cylinder bores (series production).
This insures that the specified piston clearance is maintained.
When performing repairs, all the cylinder bores should be honed to the dimensions of the existing pistons plus piston clearance (see table).
The piston pins are matched to the pistons and must not be interchanged.
The direction of travel arrow is stamped on the piston crown and is no longer visible on used engines.

REMOVING, INSTALLING





1 Unscrew conrod bearing caps and remove conrod together with pistons upward.

NOTE:
Conrod and conrod cover (arrow) are marked together.
Do not damage cylinder contact surfaces with conrod.

2 Examine conrod bolts.





3 Remove piston pin retainer with screwdriver and press out piston pin.
Do not damage pistons, use a clean cloth as a base.
4 Repair conrod and align, if necessary.





5 Check the end and axial clearance of piston rings on used pistons. Check the piston rings for ease of movement. Pay attention to install position: "Top" is at the top.
Distribute ring joints evenly around the circumference.

NOTE: Oil scraper ring (3)

The wire in the garter spring (4) of the oil scraper ring (3) has a hook (8). This hook (8) must be inserted into one of the recesses (arrow) on the oil scraper ring (3).
6 Oil piston pins and conrod bushes.





7 Install pistons so that the piston code number (5) next to the piston pin and group number (6) are pointing in the direction of travel and the identification (9) on the conrod is facing to the outside of the engine.

NOTE:
The conrods are off-center, the wide thrust collars (7) face the crankshaft webs.





8 Press in piston pins by hand.





9 Insert piston pin retainer in the groove (arrow).
10 Oil cleaned cylinder bores, conrod bearing journals, conrod bearing shells, and pistons.





11 Fit on tensioning strap (1) 000 589 04 14 00 for piston rings and insert piston into the cylinder bore with arrow or piston code number and group number facing direction of travel.
Do not damage cylinder contact surface with conrod.





12 Fit conrod bearing caps onto the conrod with the marking (arrow) facing each other. Moisten the threads and contact surfaces of the conrod bolts with engine oil and tighten.
Pay attention to installed position of conrod bearings. Install the conrod bearing shell with oil passage in the conrod otherwise lubrication of the piston pin is not assured.
Tightening torque: 40 Nm (45 Nm for initial tightening)
Tightening angle: 90-100°
13 Rotate crankshaft and check ease of movement.

TIGHTENING TORQUES IN NM






SPECIAL TOOL