11 25 530 Removing And Installing/Replacing All Pistons (S54 with M10x1.25 Conrod Bolt)

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Special Tools Required:

00 2 590
00 9 120
11 2 050
11 9 120

(Engine removed)

Removal:

Removal of pistons is described separately from installation. Assembly sequence for removal and installation is different.

Fit engine to special tool 00 1 450.

Removing cylinder head.
Removing oil pan.
Removing oil pump.

CAUTION: Re-install piston, conrod and bearing shells back in the same position and in the same installation location. Conrod and conrod bearing cover are designated with same pair number: do not interchange/confuse.

In event of heavy oil carbon residue:

Carefully remove oil carbon residue from cylinder wall.

Fig 1: View Of Oil Carbon Residue From Cylinder Wall

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NOTE: Piston cooling spray nozzles are installed between the bearing seats.

Check spray nozzles for damage.

If necessary, remove piston-cooling spray nozzles.

Fig 2: Identifying Piston Cooling Spray Nozzles

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CAUTION: The S54 engine has two types of conrod with different conrod bolts.

Differentiating Features:

A Conrod bolt with M11x1.25 thread. Bolt head: bihexagonal 12 mm A/F.
B Conrod bolt with M10x1.25 thread. Bolt head: Torx E12.

The procedure for replacing the conrod bolts and the tightening specifications are different.

Mixing up the procedure for replacing the conrods and conrod bolts and the tightening specifications will result in serious engine damage.

Fig 3: Identifying Types Of Conrod Bolts

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CAUTION: In the S54 engine with the M10x1.25 conrod bolt (B) the conrod bolts must be replaced.

Conrod bolts (B) are made from a material which only reaches its maximum tensile strength after they have been tightened three times.

Connecting rod bolts (B) must be tightened at least three times but no more than five times.

Fig 4: Identifying M10x1.25 Conrod Bolt

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Release conrod bolts.
Remove conrod bearing cap.
Set conrod bolts and conrod bear caps down in neat order.

Fig 5: Locating M10x1.25 Conrod Bolt

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Insert special tool 11 2 050 in conrod.

Remove connecting rod with piston from cylinder-head side.

Fig 6: Identifying Special Tool 11 2 050 In Conrod

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CAUTION: Piston and piston bolts are paired and must not be fitted individually.

Lift out retaining ring and press out piston pin.

Fig 7: Removing Retaining Ring & Piston Pin

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Installation:

Installation of pistons is described separately from removal. The assembly sequence for removal and installation is different.

The piston pin must be able to be pressed through the liner by hand with little force and must not display any significant play. If necessary, replace connecting rods.

Fig 8: Identifying Piston Pin

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NOTE: Only conrods of the same weight group are allowed to be installed inside an engine. Connecting rods are only supplied in complete sets.

Prior to installation, 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. For measuring point A, refer to 11 25 Pistons With Rings And Pins S54, in ENGINE - TECHNICAL DATA .

Fig 9: Locating Measuring Point

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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.

Fig 10: Measuring Cylinder Bore

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Diameter of cylinder bore, refer to 11 00 Engine In General S54 in ENGINE - TECHNICAL DATA .
Piston installation clearance, refer to 11 25 Pistons With Rings And Pins S54 in ENGINE - TECHNICAL DATA .
Permitted total wear clearance, refer to 11 25 Pistons With Rings And Pins S54 in ENGINE - TECHNICAL DATA .

CAUTION: Piston and piston pins are paired and must not be fitted individually.

Fit conrod with piston pin to piston in such a way that both of the visible pair numbers on the installation direction arrow on the piston point to the right.

Fig 11: Identifying Conrod Pair Numbers

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Install retaining ring.

Fig 12: Installing Retaining Ring

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CAUTION: Note grinding stages on crankshaft. Refer to 11 21 Crankshaft And Bearings S54 in ENGINE - TECHNICAL DATA .

NOTE: Classified conrod bearing shells color-coded "Yellow and Green" are installed in the model series. The classification is removed when the conrod bearing shells are replaced.

Install conrod bearing shells (1) color-coded "Blue" in conrod at top.
Install conrod bearing shells (2) color-coded "Red" in conrod at top.

Fig 13: Identifying Conrod Bearing Shells

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Insert special tool 11 2 050 in conrod.

Lightly coat pistons and piston rings with oil.

Offset the contact points of the piston rings by approx. 120° to each other but do not position above the piston pin boss.

Compress piston rings with special tool 11 9 120.

Fig 14: Compressing Piston Rings

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Keep piston rings pressed with special tool 11 9 120. Install piston so that arrow points to camshaft drive.

CAUTION: Danger of piston ring failure. Only press pistons into place with finger force - do not knock in!

Fig 15: Installing Piston

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Attach crankpin to connecting rod.

Remove special tool 11 2 050.

Fig 16: Removing M10x1.25 Conrod Bolt Connecting Rod

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Conrod With M10X1.25 Conrod Bolt:

CAUTION: Conrod bolts (B) are made from a material which only reaches its maximum tensile strength after they have been tightened three times. Connecting rod bolts (B) must be tightened at least three times but no more than five times. The tightening specifications detailed in the following must be observed exactly. Mixing up the procedure for replacing the conrods and conrod bolts and the tightening specifications will result in serious engine damage.

Fig 17: Identifying M10x1.25 Conrod Bolt

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Check connecting rod bearing clearance:

Piston in BDC position.

Fit special tool 00 2 590 (Plastigage Type PG 1) to the oil-free crankshaft.

Fig 18: Checking Connection Rod Bearing Clearance

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Fit bearing caps so that pair numbers match up.

Fig 19: View Of Bearing Cap Pair Numbers

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Conrod With M10X1.25 Conrod Bolt:

If A New Set Of Conrods Has Been Installed:

Use the conrod bolts used in the new set of conrods.

If The Conrods Already Used Have Been Installed:

Install new conrod bolts.

Fig 20: View Of M10x1.25 Conrod Bolt

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Conrod With M10X1.25 Conrod Bolt:

CAUTION: Do not distort conrods or crankshaft.

First Tightening Of Conrod Bolts:

Tighten down conrod bolts with special tool 00 9 120.

Tightening torque:

Application torque 5 N.m.
Joining torque 30 N.m.
Angle of rotation 105°.

Fig 21: Tightening Conrod Bolts

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Remove bearing cap and read off bearing play at width of flattened plastic thread with assistance of measurement scale.

Conrod Bearing Clearance: 0.030 To 0.070 mm.

Fig 22: Measuring Bearing Clearance

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Remove plastic thread.
Coat crankshaft and bearing shells with oil.
Fit bearing caps so that the pair numbers match up.
Fit the conrod bolts used for the bearing clearance.

Fig 23: View Of M10x1.25 Conrod Bolt

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Conrod With M10X1.25 Conrod Bolt:

Second Tightening Of Conrod Bolts:

Tighten down conrod bolts with special tool 00 9 120.

Tightening torque:

Application torque 5 N.m.
Joining torque 30 N.m.
Angle of rotation 105°.

Fig 24: Tightening Conrod Bolts

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CAUTION: The following work step differs depending on whether a new set of conrods has been fitted or only the conrod bolts have been replaced. If A New Set Of Conrods Has Been Installed: The conrod bolts must not be tightened down again as they have already been screwed down three times when the conrod was machined and have reached their maximum tensile strength. If The Conrods Are Reused And Only The Conrod Bolts Have Been Replaced: The conrod bolts must be slackened again and brought to maximum tensile strength by the third tightening operation. If the conrod bolts have not been tightened at least three times or have been tightened more than five times, this will result in serious engine damage.

If necessary, back off conrod bolts by approx. one turn.

Third Tightening Of Conrod Bolts:

Tighten down conrod bolts with special tool 00 9 120.

Tightening torque:

Application torque 5 N.m.
Joining torque 30 N.m.
Angle of rotation 105°.

Install spray nozzles for piston cooling, tighten down screw.

Tightening torque, 11 11 7AZ. Refer to ENGINE - TIGHTENING TORQUES .

Fig 25: Identifying Piston Cooling Spray Nozzles

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