Piston: Service and Repair

Pistons and Connecting Rod Assembly Overview

• Oil injector jet for piston cooling => [ Oil Spray Jet For Piston Cooling ].





1 Bolt

• Replace

• Lubricate threads and contact surface

• 50 Nm plus an additional 90° turn

• Tighten to 50 Nm to measure radial play, do not turn further

2 Connecting Rod Bearing Cap

• Do not interchange

• Mark affiliation to cylinder with paint.
.
3 Bearing Shells

• Check that retaining tabs are secured

• Do not interchange used bearing shells (mark, but not on the running surface)

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

• To measure radial play, tighten bolts item - 1 - to 60 Nm but no further

• Oversized bearings are available for reworked crankshaft connecting rod journals

4 Connecting Rod

• Only replace as set

• Mark affiliation to cylinder with paint.
.
• Axial play for each new connecting rod pair: 0.20 to 0.27 mm

• Axial play wear limit: 0.30 mm

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

5 Piston Pin

• If tight, heat piston to 60 °C / 140 °F

• Removing and installing using a drift (VW 222 A)

6 Circlip

• Replace

7 Piston
.
• Piston and cylinder dimension, piston allocation to cylinder bore, 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 removal and installation

• "TOP" marking or inscribed side must point to piston head

Piston Ring End Gap, Measuring





- Slide piston ring down from above at a right angle to cylinder wall until it is approximately 15 mm from bottom edge of cylinder.

- When sliding in, use a piston without piston rings.






Measuring Piston Ring Side Clearance





- Clean the ring groove of piston before checking.






Pistons, Checking





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

• 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 - using a cylinder gauge (VAS 6078).

• 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 crown with a punch, notch or similar object.

Installation position:

• Arrows on piston heads point to belt pulley side.

• Large valve recesses - 1 - point toward center of engine.

Mark Connecting Rod





• Only replace connecting rod as a set.

• Do not interchange connecting rod bearings.

- Mark connecting rod and connecting rod bearing cap to each other and to cylinder - arrow - with paint before removal.

Connecting Rod, Installed Location





• Molded tabs - arrows - at the beveled surfaces of the connecting rod pairs 1 and 2, 3 and 4, 5 and 6 as well as 7 and 8 must point toward each other.

Oil Spray Jet For Piston Cooling





1. Oil spray jet

2. Bolts - 9 Nm. Insert with locking compound; Locking compound.

• Do not bend piston spray nozzles.

• Bend piston spray nozzles must be replaced.