Piston: Service and Repair

Pistons and Connecting Rod Overview

• Lubricate all bearings and running surfaces.

• Oil injector jet for piston cooling.






1 Bolts

• 50 Nm plus an additional 90° turn

• Replace

• Lubricate the threads and contact surface

2 Connecting Rod Bearing Cap

• Mark for installation later

• Mark affiliation to cylinder with paint.
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3 Bearing Shells

• Check that retaining tabs are secured

• Replace any worn bearing shells

• Over-sized bearings are available for reworked crankshaft connecting rod journals, refer to the Parts Catalog

• The connecting rod tabs are above each other

4 Connecting Rod

• Only replace as a set

• Mark affiliation to cylinder with paint.
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• Axial play for each new connecting rod pair: 0.20 to 0.45 mm

• Radial clearance, measuring, refer to => [ Connecting Rod, Measuring Radial Clearance ] Testing and Inspection

5 Locking Ring

• Replace

6 Piston Pin

• Heat piston to 60 °C (140 °F) if it is difficult to move.

• Removing and installing with the pilot drift (VW 222 A)

7 Piston

• Mark the installation position and cylinder allocation.

• Replace the piston if there are cracks on the piston head or piston shaft

• For the correct piston and cylinder dimensions, refer to => [ Piston and Cylinder Dimensions ] [1][2]Piston, Engine

• Install with piston ring compressor

8 Piston Rings

• Offset gaps by 120°

• Use piston ring pliers for removing and installing

• Installed position: The "TOP" marking or side with writing faces the piston crown.

Piston Ring End Gap, Measuring





- Push the piston ring squarely from above down to approximately 15 mm from the bottom end of the cylinder.

- Use a piston without a piston ring for sliding in.






Measuring Piston Ring Side Clearance





- Clean the piston ring groove before checking.






Pistons, Checking





- Measure approximately 15 mm from the lower edge at a 90° angle to the piston pin axis using a 75 to 100 mm external micrometer.

• Maximum deviation from nominal dimension: 0.03 mm.

Nominal dimension, refer to => [ Piston and Cylinder Dimensions ] [1][2]Piston, Engine.

Measuring Cylinder Bore





- Measure diagonally at 3 positions transversely - A - and longitudinally - B - with a cylinder gauge (VAS 6078) or inside micrometer set 18-100 mm (US1033/S).

• Maximum deviation from nominal dimension: 0.08 mm.

Nominal dimension, refer to => [ Piston and Cylinder Dimensions ] [1][2]Piston, Engine.

Piston Installation Position





The coating on the piston crown could be destroyed.

• Mark the allocation to the cylinder on the piston crown with paint to install used pistons. Do not mark the piston head with a punch, notch or something similar.

Installed position:

• The arrows on the piston heads point to the belt pulley side.

Mark Connecting Rod





• Only replace connecting rod as a set.

• Do not interchange connecting rod bearings.

- Mark the connecting rod and connector rod bearing caps to each other and to the cylinder - arrow - with paint for installation.

Connecting Rod, Installed Location





• The molded tabs - arrows - on the beveled surfaces of the connecting rod pairs "1 and 2", "3 and 4" and "5 and 6" must face each other.

Oil Spray Jet for Piston Cooling





1. Insert the bolt with locking compound and tighten to 9 Nm; locking compound, refer to the Parts Catalog.

2. Oil spray jet with spray nozzle valve (opening pressure 2 to 2.4 bar)


• Do not bend piston spray nozzles.

• Bend piston spray nozzles must be replaced.