11 25 530 Removing And Installing/Replacing All Pistons (S85)

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Special tools required:

00 9 120
11 4 492
11 5 250
11 5 341
11 5 342
11 5 343
11 5 344
11 9 500
12 2 100

WARNING: Protective goggles must be worn when working on the piston pin circlip.

IMPORTANT: If pistons, conrods and bearing shells are reused, they must be reinstalled in the same places.
Piston and piston pin are matched to each other and can only be replaced as a pair.
Connecting rod and connecting rod bearing cap are cracked.
Identification is effected by means of identical pairing letters on the connecting rod big end.
Mixing up the components will result in engine damage.
Setting of special tool 115 343 must not be altered.

Necessary preliminary tasks:

Remove engine .
Mount engine on assembly stand .
Remove intake air manifold .
Remove left cylinder head or right cylinder head .
Remove engine oil sump .
Remove oil pump .
Remove VANOS high-pressure pump .

Do not bend oil nozzle (2) at outlets.

It is not possible to adjust the nozzles.

Oil nozzle (2) must be replaced if it is maladjusted or bent.

Release screws (1).

Oil nozzle (2)

Fig 1: Identifying Oil Nozzle

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Release connecting rod bolts (1) with special tool 12 2 100.

Remove connecting rod bearing cap with bearing shell.

Fig 2: Identifying Connecting Rod Bolts And Special Tool 12 2 100

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Special tool 11 5 250 without locating rod must be screwed in on the connecting rod at the bottom.

Special tool 11 5 250 with locating rod must be screwed in on the connecting rod at the top.

Fig 3: Identifying Special Tool 11 5 250

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Rotate crankshaft (1) in direction of arrow, risk of damage to special tool 11 5 250.

Remove piston with connecting rod and special tool 11 5 250.

Depiction of function on cylinders 1-5.

IMPORTANT: Risk of damage to oil nozzle.

Fig 4: Rotating Crankshaft

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Clamp special tool 11 5 341 in a vice.

NOTE: Piston and piston pin are optimized to each other.
There are two different inside diameters on the piston pin.

Screw matching special tool 11 5 342 into special tool 11 5 341.

Fig 5: Identifying Special Tool 11 5 341 And 11 5 342

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Secure piston (1) with conrod to special tool 11 5 341.

Fig 6: Securing Piston With Conrod To Special Tool 11 5 341

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WARNING: Protective goggles must be worn for the next work step.

WARNING: Protective goggles must be worn.

Lever out piston circlip with special tool 11 4 492 in direction of arrow.

Fig 7: Levering Out Piston Circlip With Special Tool 11 4 492

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If necessary, replace connecting rods.

Installation:

The piston pin must be able to be pressed through the liner by hand with little force and must not display any significant play.

Fig 8: Pressing Piston Pin

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Measure 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 piston pin.

Piston diameter at measuring point A.

Fig 9: Measuring Piston Diameter

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Adjust micrometer to cylinder bore of engine block. Set internal caliper on micrometer to zero. Measure bottom, center 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.

If necessary, replace piston.

Fig 10: Measuring Cylinder Bore

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IMPORTANT: The connecting rods are not symmetrical.
Pay attention to elevation to direction of travel arrow.

Fig 11: Identifying Connecting Rod Elevation

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Make sure the connecting rod is in the correct installation position during preliminary installation.

On cylinders 6-10 the elevation (2) must point forwards with the arrow.

On cylinders 1 -5 the elevation (1) must point rearwards against the arrow.

Valve pockets (E) point to inlet side.

Arrow direction is identical to direction of travel.

Fig 12: Identifying Connecting Rod Elevation - Cylinders 6-10 And 1-5 (1 Of 2)

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On cylinders 6-10 the elevation must point forwards with the arrow.

On cylinders 1-5 the elevation (1) must point rearwards against the arrow.

IMPORTANT: No elevations on the connecting rod big end are permitted to point to each other during installation, risk of damage to connecting rod.

Fig 13: Identifying Connecting Rod Elevation - Cylinders 6-10 And 1-5 (2 Of 2)

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Secure piston (1) with conrod to special tool 11 5 341.

Fig 14: Securing Piston With Conrod To Special Tool 11 5 341

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WARNING: Protective goggles must be worn.

IMPORTANT: Setting of special tool 11 5 343 must not be altered.

Installation:

Insert piston circlip (2) so that opening points to window.

Insert piston circlip (2) into groove (1) of special tool 11 5 343.

NOTE: Illustration shows N52.

Fig 15: Identifying Piston Circlip And Special Tool 11 5 343

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Position special tool 11 5 343 with window to opening on piston (see arrow).

Fig 16: Positioning Special Tool 11 5 343 With Window To Opening On Piston (1 Of 2)

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Position special tool 11 5 343 with window to opening on piston (see arrow).

Fig 17: Positioning Special Tool 11 5 343 With Window To Opening On Piston (2 Of 2)

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WARNING: Protective goggles must be worn.

Guide lug and cutout on special tool 11 5 343 must point to piston crown.

When special tools 11 5 343 and 11 5 344 are correctly positioned, the piston circlip must be driven in with a plastic hammer in the direction of the arrow.

Fig 18: Driving In Piston Circlip

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Installation:

Piston circlip (1) is correctly installed when the opening points upwards.

It must still be possible for piston pin to moved easily

Fig 19: Installing Piston Circlip

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Install all piston rings.

Install all bearing shells.

Screw special tool 11 5 250 into connecting rod.

Always screw in special tool 11 5 250 with rod to exhaust side.

Preinstall piston with piston rings in special tool 11 9 500.

Fig 20: Identifying Special Tool 11 5 250

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Insert piston with conrod in cylinder.

IMPORTANT: Risk of damage to oil spray nozzle.
Danger of piston ring failure.

Insert piston so that arrow (direction of travel pointing forwards) on piston crown points to camshaft drive.

Piston cyl. 1-5 right side, cyl. 6-10 left side.

Press in piston with special tool 119 500.

Fig 21: Identifying Special Tool 119 500

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IMPORTANT: Conrod and conrod bearing cap are identified with pairing letters (1) and must not be mixed up.
Mixing them up or incorrectly fitting the conrod bearing cap on the big end will result in engine damage .

Fig 22: Identifying Connecting Rod With Pairing Letters

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IMPORTANT: Risk of damage to oil nozzle.

Rotate crankshaft (1) in direction of arrow, risk of damage to special tool 11 5 250.

Insert piston with connecting rod and special tool 11 5 250.

NOTE: Depiction of function on cylinders 1-5.

Fig 23: Rotating Crankshaft

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Moisten conrod bearing shell and crank pin slightly with engine oil.

Assemble conrod and crank pin.

Remove special tool 11 5 250.

Fig 24: Identifying Special Tool 11 5 250

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Install connecting rod bearing cap with bearing shell.

Secure connecting rod bolts (1) with special tools 12 2 100 and 00 9 120.

Tightening torque 11 24 1AZ. See CONNECTING RODS AND BEARINGS .

Fig 25: Identifying Connecting Rod Bolts And Special Tools 12 2 100

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Assemble engine.