Necessary preliminary tasks

Fully remove front axle together with engine.
Remove ENGINE from front axle.
Install engine on assembly stand.
Remove LEFT CYLINDER HEAD .
Remove RIGHT CYLINDER HEAD .
Removing oil sump. See LOWER OIL SUMP SECTION and UPPER OIL SUMP SECTION .
Remove OIL PUMP .

To release the connecting rod bolts (1), the crankshaft (2) must be moved to a suitable position.

Release connecting rod bolts (1).

Fig 1: Identifying Connecting Rod Bolts And Crankshaft

Screw the special tool 2 249 164 (assembly tool) into the connecting rod.

Fig 2: Identifying Special Tool 2 249 164 Secured To Connecting Rod

NOTE: For installation and dismantling of the connecting rods, it is essential for the crankshaft to be exactly in alignment with the cylinder bore.

Position crankshaft at central bolt.

Insert special tool 11 8 152 into conrod.

Press out the connecting rod and piston with special tool 22 49 164 towards the cylinder head side.

Fig 3: Removing Conrod With Piston From Cylinder Head Side

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IMPORTANT: Pistons and gudgeon pins are paired and must not be fitted individually.

Lift out circlip and press out piston pin.

Fig 4: Removing Retaining Ring From Piston

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If necessary, replace connecting rods.

NOTE: The connecting rod can also be replaced individually.
The gudgeon pin must be able to be pressed through the bush by hand with little force and must not display any significant play.

Fig 5: Installing Gudgeon Pin

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Prior to installation, measure piston installation clearance: Measure piston diameter with micrometer at measuring point A from lower edge of piston and offset at 90° to the axis of the gudgeon pin.

Refer to MEASURING POINT A .

Fig 6: Measuring Piston Diameter

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Adjust micrometer to cylinder bore of engine block. Set internal calliper on micrometer to zero. Measure bottom, center and top of cylinder bore in direction of travel and direction of engine rotation.

Refer to:

Fig 7: Checking Diameter Of Cylinder Bore

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Installation note:

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

See illustration.

It must still be possible for the gudgeon pin to be moved easily.

Fig 8: Locating Piston Circlip

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Insert the special tools 22 49 164 (assembly tool) into the connecting rod.

Install CONNECTING ROD BEARING .

Fig 9: Inserting Special Tools 11 8 151 And 11 8 152 Into Conrod

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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.

NOTE: Illustration shows S85.

Fig 10: Identifying Piston Rings Offset Contact Points

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Keep piston rods compressed with special tool 11 7 280 .

Install piston so that arrow points to camshaft drive.

IMPORTANT: Risk of piston ring breakage.

Press in piston only with finger force (do not knock in!).

Fig 11: Compressing Piston Rods With Special Tool 11 7 280

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The direction arrow on the piston crown must point to the camshaft drive (direction of travel towards front).

Fig 12: Identifying Piston Crown Direction

Connect the crankshaft journal to connecting rod.

Remove special tools 22 49 164.

Fig 13: Connecting Crankshaft Journal And Connecting Rod And Removing Special Tools 22 49 164

NOTE: For purposes of clarity, the pairing letters (1) are shown on the removed connecting rod.

IMPORTANT: Connecting rods and connecting rod bearing caps are denoted with the same pairing letters (1), do not mix them up.
Fit bearing cap so that pairing letters match up.

Fig 14: Identifying Conrods And Conrod Bearing Caps Pairing Letters

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Apply light coat of oil to connecting rod bearing shells.

Fit bearing cap so that pairing letters match up.

Install new connecting rod bolts.

Fig 15: Locating Conrod Bolts

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Tighten down connecting rod bolts (1) with special tool 00 9 120 .

Tightening torque 11 24 1 AZ .

Fig 16: Tightening Down Connecting Rod Bolts With Special Tool 00 9 120

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