Piston: Service and Repair
11 25 530 - Removing and installing/replacing all pistons (N54)
Special tools required:
- 00 9 120 00 9 120 Torque Angle Measuring Dial
- 11 5 464 11 5 464 Removal Pliers
- 11 8 141
- 11 8 560 11 8 560 Tool Set
- 11 8 561
- 11 8 562
- 11 8 563
- 11 8 590 11 8 590 Assembly Tool
Warning!
Protective goggles must be worn when working on the piston pin circlip.
Important!
If pistons, connecting rods and bearing shells are reused, they must be reinstalled in the same places.
Individual connecting rod replacement is not permitted; they are classified according to weight categories.
Connecting rods and connecting rod bearing caps are marked with the same pairing letters; mixing them up will result in engine damage.
Piston and gudgeon pins are paired and must not be fitted individually.
Necessary preliminary tasks:
- Remove engine Removing and Installing Engine
- Mount engine on assembly stand 11 00 ... Mounting Engine on Assembly Stand
- Remove intake air manifold Service and Repair
- Remove cylinder head Removal and Replacement
- Remove oil sump
- Remove oil pump 11 41 000 Removing and Installing/Replacing Oil Pump
Note:
In event of heavy oil carbon residue:
Carefully remove oil carbon residue from cylinder wall.
Note:
Illustrations show N46.
Do not release screw (1).
Oil spray nozzle Service and Repair(2) must not be maladjusted or bent.
If necessary, readjust (risk of damage).
Release connecting rod bolts (1).
Tightening torque 11 24 1AZ. Mechanical Specifications
Remove connecting rod bearing cap (2) in direction of arrow.
Important!
Connecting rods and connecting rod bearing caps are marked with the same pairing letters; mixing them up will result in engine damage.
Screw special tool 11 8 590 into base of connecting rod.
Press out connecting rod and piston to cylinder head side.
Important!
Risk of damage to oil spray nozzle.
Preliminary work:
Clamp special tool 11 8 561 in a vice.
Secure piston (1) with connecting rod to special tool 11 8 561.
Warning!
Protective goggles must be worn for the next work step.
Warning!
Protective goggles must be worn.
To lever out piston circlip (1), support special tool 11 5 464 on piston (2).
Lever out piston circlip (1) with special tool 11 5 464 in direction of arrow.
Installation Note:
If necessary, replace connecting rods.
Important!
Connecting rods are divided into weight categories and are only available as a set.
Old and new connecting rods must not be installed in mixed combinations.
Installation Note:
The gudgeon pin must be able to be pressed through the liner by hand with little force and must not display any significant play.
Measuring piston installation clearance:
Measure piston diameter with micrometer at measuring point A from bottom edge of piston and offset at 90° to the axis of the gudgeon pin.
Piston diameter at measuring point A.
Adjust micrometer to cylinder bore of engine block. Set internal calliper on micrometer to zero. Measure bottom, centre and top of cylinder bore in direction of travel and direction of engine rotation.
Diameter of cylinder bore.
Piston installation clearance.
Total permissible wear tolerance .
Installation Note:
If necessary, replace piston.
Warning!
Protective goggles must be worn.
Important!
The opening of the piston pin circlip must be installed in the 6 o'clock position on the piston.
Risk of damage!
Insert piston circlip (2) into groove of special tool 11 8 562.
Bring piston circlip (2) into assembly position (1).
Warning!
Protective goggles must be worn.
Slide special tool 11 8 563 up to piston pin circlip (2)
Special tools 11 8 562 and 11 8 563 are prepared.
Warning!
Protective goggles must be worn.
Cutout on special tool 11 8 562 must point to piston crown; only then can special tool 11 8 563 be correctly fitted.
When special tools 11 8 562 and 11 8 563 are correctly positioned, the piston pin circlip must be driven in with a plastic hammer in the direction of the arrow.
Note:
See illustration.
Piston pin circlip is correctly installed when opening (1) points downwards.
Note:
B 30.
Install all piston rings.
Install all bearing shells.
Coat piston and piston rings with oil.
Pre-install piston (2) in special tool 11 8 141.
Screw on special tool 11 8 590 in connecting rod (2).
Installation Note:
Check protective lugs (1) on special tool 11 8 590 for correct position and damage.
Insert piston with connecting rod in cylinder.
Important!
Risk of damage to oil spray nozzle.
Danger of piston ring failure.
Press in piston in direction of arrow with finger pressure only, do not drive in.
Insert piston so that arrow on piston crown points to camshaft drive.
Press in piston (1) with special tool 11 8 141.
Important!
Connecting rod and connecting rod bearing cap are marked with pairing letters (1) and must not be mixed up.
Mixing them up or incorrectly fitting the connecting rod bearing cap on the big end will result in engine damage.
Apply a light coat of oil to crank pin.
Assemble connecting rod and crank pin.
Screw off special tool 11 8 560 in counterclockwise direction.
Fit bearing caps (2) so that pairing letters match up.
Install new connecting rod bolts (1).
Tightening torque 11 24 1AZ. Mechanical Specifications
Adjust torsion angle of conrod with special tool 00 9 120 (see illustration).
Tightening torque 11 24 1AZ. Mechanical Specifications
Assemble engine.