Piston: Service and Repair

Pistons and connecting rods, disassembling and assembling
1. 30 Nm + 1/4 turn (90°) further
^ Replace connecting rod bolt - 13 -
^ Oil threads and contact surface
^ To measure radial clearance, tighten to 30 Nm but not further
2. Pressure relief valve, 27 Nm
^ Opens at: 2.5 - 3.2 bar
3. Oil spray jet
^ For piston cooling
4. Connecting rod bearing cap
^ Mark cylinder number -B
^ Installation position: Marking -A- must face toward pulley end
5. Bearing shell
^ Note installation position
^ Do not interchange used bearing shells (mark)
^ Make sure that bearing shell is seated correctly in retaining lugs
^ Axial clearance:
- New: 0.1 - 0.35 mm
- Wear limit: 0.40 mm
^ Check radial clearance with Plastigage
- New: 0.01 - 0.05 mm
- Wear limit: 0.12 mm
^ Do not rotate crankshaft when checking radial clearance
^ To measure radial clearance, tighten nut -1- to 30 Nm but not further
6. Cylinder block
^ Checking cylinder bore - Fig 4
^ Piston and cylinder dimensions, Refer to Piston, Engine, Specifications
7. Bearing shell
^ With oil drilling for piston pin lubrication
^ Note installation position
^ Do not interchange used bearing shells (mark)
^ Axial clearance
- New: 0.1 - 0.35 mm
- Wear limit: 0.40 mm
^ Check radial clearance with Plastigage
- New: 0.01 - 0.05 mm
- Wear limit: 0.12 mm
^ Do not rotate crankshaft when checking radial clearance
^ To measure radial clearance, tighten nut -1 to 30 Nm but not further
8. Connecting rod
^ Only replace as set
^ Mark cylinder number -B
^ Installation position: Marking -A- must face toward pulley end
^ With oil drilling for piston pin lubrication
9. Circlip
10. Piston pin
^ If difficult to move, heat piston to approximately 60°C
^ Remove and install with VW 222a
11. Piston rings
^ Offset gaps by 120 -
^ Remove and install with piston ring pliers
^ "TOP" must face toward piston crown
^ Checking ring gap, Refer to Fig 1
^ Checking ring to groove clearance, Refer to Fig 2
12. Piston
^ Mark installation position and cylinder number
^ Arrow on piston crown must point to pulley end
^ Install using piston ring clamp
13. Connecting rod bolt
^ Replace








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








Fig. 2 Checking ring to groove clearance
^ Clean groove before checking clearance.





Fig. 3 Checking piston
^ Measure pistons approximately 10 mm from lower edge of skirt, at 90° to piston pin axis.
^ Deviation from nominal dimension: maximum 0.04 mm

Fig. 4 Checking cylinder bore
Special tools and repair equipment required





^ Internal dial gauge 50...100 mm
^ Take measurements at 3 positions in both lateral -A- and longitudinal -B- directions.
^ Deviation from nominal dimension: maximum 0.08 mm