Piston: Service and Repair

Pistons and Connecting Rod Overview






1 Connecting Rod Bolt

• Replace

• 30 Nm plus an additional 90° (1/4 turn)

• Lubricate threads and contact surface

• Use old bolt to measure radial play

• Tighten to 30 Nm to measure radial play, do not turn further

2 Pressure Relief Valve

27 Nm

• Opening pressure 1.6 to 1.9 bar

3 Oil Spray Jet

• For piston cooling

4 Connecting Rod Bearing Cap

• Pay attention to the installed position

• Due to the separation procedure (cracking) of the connecting rod, the cap only fits in one position and only to the corresponding connecting rod.

• Affiliation to the cylinder mark - B -

• Installation position: Markings - A - point to belt pulley side

5 Bearing Shells

• Upper bearing shell with oil hole for piston pin lubrication

• Installed location, refer to => [ Installed Position of Bearing Shell ]

• Do not interchange used bearing shells (mark)

• Axial play new: 0.10 to 0.35 mm Wear limit: 0.40 mm

• Measure radial clearance with Plastigage: New: 0.02 to 0.06 mm; Wear limit: 0.09 mm. Do not turn crankshaft when checking radial clearance

6 Connecting Rod

• Only replace as set

• Affiliation to the cylinder mark - B -

• Installation position: Markings - A - point to belt pulley side

• With oil hole for piston pin lubrication

7 Circlip

8 Piston Pin

• If difficult to move, heat piston to approximately 60 °C (140 °F)

• Use pilot drift (VW 222 A) for removal and installation

9 Piston

• Checking, refer to => [ Pistons, Checking ]

• Mark installed position and cylinder allocation

• Arrow on piston face points toward belt pulley side

• Install with piston ring compressor

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

• Cylinder bore, checking, refer to => [ Cylinder Bore, Checking ]

10 Piston Rings

• Offset gaps by 120°

• Use piston ring pliers for removing and installing

• "TOP" mark must face up toward piston crown

• Checking ring gap, refer to => [ Piston Ring Gap, Checking ]

• Check piston ring groove clearance, refer to => [ Piston Ring Groove Clearance, Checking ]

Piston Ring Gap, Checking





- Push ring squarely from above down to approximately 15 mm from bottom end of cylinder. To do this use a piston without rings.






Piston Ring Groove Clearance, Checking





- Clean the ring groove of piston before checking.






Pistons, Checking





- Measure pistons approximately 10 mm from bottom edge and at points offset by 90° to piston pin axis.

• Deviation from nominal size: max. 0.04 mm.

Cylinder Bore, Checking





Special tools, testers and auxiliary items required

• Internal dial gauge 50 to 100 mm.

• Inside Micrometer Set 18-100 mm (US1033/S)

- Measure diagonally at 3 positions transversely - A - and longitudinally - B -.

• Deviation from nominal size: max. 0.08 mm.

Installed Position of Bearing Shell





Bearing shell - 1 - with connecting rod oil bore - arrow -.

Bearing shell - 2 - without connected rod cover oil bore.

- Place bearing shells centrally into connecting rod and connecting rod cover.

Dimension - a - must be the same at left and right.