Piston: Service and Repair

Piston and connecting rods, disassembling and assembling

Note: Oil spray jet and pressure relief valve Refer to, Fig. 6

1. Connecting Rod bolt - 30 Nm + 1/4 turn (90°) further
^ Always replace
^ Oil threads and contact surface
^ To measure radial clearance use old bolt
^ To measure radial clearance tighten to 30 Nm but not further
2. Connecting Rod bolt bearing cap
^ Mark cylinder number -B-
^ Installation position: Markings -A- face towards pulley side
3. Bearing shells
^ Upper bearing shell with oil bore for piston bolt lubrication
^ Installation position Refer to, Fig. 5
^ Do not interchange used bearing shells (mark).
^ Axial clearance New: 0.10 to 0.35 mm, Wear limit: 0.40 mm
^ Check radial clearance with Plastigage: New: 0.01 to 0.05 mm, Wear limit: 0.12 mm. Do not rotate crankshaft when checking radial clearance
4. Connecting Rod bolt
Only replace as a set
^ Mark cylinder number -B-
^ Installation position: Markings -A- face toward pulley side
^ With oil bore for piston pin lubrication
5. Circlip
6. Piston pin
^ If difficult to remove, heat piston to approximately 60°C
^ Remove and install with VW 222a
7. Piston
^ Checking Refer to, Fig. 3.
^ Mark installation position and cylinder number.
^ Arrow on piston crown points to pulley end
^ Install using piston ring clamp.
^ Piston and cylinder dimensions
8. Piston rings
^ Offset gaps by 120°
^ Remove and install with piston ring pliers.
^ "TOP" must face piston crown
^ Check ring gap Refer to, Fig. 1.
^ Check ring to groove clearance Refer to, Fig. 2.





Fig. 1 Checking piston ring gap
^ Push ring squarely from above down to approximately 15 mm from bottom end of cylinder. To do this, use a piston without rings.

Checking Piston Ring Gap (Part 1 Of 1):

Fig. 2 Checking ring to groove clearance





^ Clean groove before checking clearance.

Piston Ring to Groove Clearance (Part 1 Of 2):

Piston Ring to Groove Clearance (Part 2 Of 2):

Fig. 3 Checking piston
^ Measure pistons approximately 10 mm from lower edge of skirt, at 90° to piston pin axis.
- Permissible deviation from nominal dimension: no more than 0.04 mm





Fig. 4 Checking cylinder bores
Special tools and equipment
^ Use internal dial gauge 50 to 100 mm
^ Take measurements at 3 positions in both lateral direction -A- and longitudinal direction B-.
- Permissible deviation from nominal dimension: no more than 0.08 mm





Fig. 5 Location of bearing shell
^ Install bearing shells centrally into Connecting rod or into Connecting rod bearing cap.
- Distance a = 3.0 mm





Fig. 6 Oil spray jet and pressure relief valve
1 - Oil spray jet (for piston cooling)
2 - Bolt with pressure relief valve - 27 Nm
^ Opening pressure 1.3 to 1.6 bar