Piston: Service and Repair

Pistons and Connecting Rod, Assembly Overview





1 Connecting rod bolt

• M8: 30 Nm + 90° turn further

• M9: 45 Nm + 90° turn further

• Replace

• Lubricate threads and contact surface

• use old bolt to measure radial play

• do not tighten 90° further when measuring radial play

2 Connecting rod bearing cap

• Note installation 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.

• Mark affiliation to cylinder - A -

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

3 Bearing shells

• Installed location => [ 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

4 Pressure relief valve

• 27 Nm

• Opening pressure: 1.6 to 1.9 bar

5 Oil spray jet

• For piston cooling

6 Circlip

7 Piston pin

• If difficult to move, heat piston to approximately 60 °C

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

8 Piston

• checking => [ Pistons, Checking ]

• Mark installed position and cylinder allocation

• Arrow on piston face points toward belt pulley side

• Install with piston ring compressor

• Piston and cylinder dimensions => [ Piston and Cylinder Dimensions ] Specifications

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

9 compression rings

• Offset gaps by 120°

• use piston ring pliers for removal and installation

• "TOP" mark must face up toward piston crown

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

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

10 Oil scraping ring

• 2-part

• Install upper steel ring so gap is offset by 120° to neighboring compression ring

• Offset all oil scraping ring component gaps to each other.

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

• Side clearance cannot be measured.

11 Connecting rod

• only replace as set

• Mark affiliation to cylinder - A -

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

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 dimension: max. 0.04 mm

Cylinder Bore, Checking





Special tools, testers and auxiliary items required

• Internal dial gauge 50 - 100 mm

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

• Deviation from nominal dimension: max. 0.08 mm

• Measurement of cylinder bore may not be performed when the cylinder block is mounted in Engine and Transmission Holder (VAS 6095), false measurements are possible.

Installed position of bearing shell





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

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