Cylinder Block Assembly: Service and Repair
Piston and connecting rod, disassembling and assembling
Gradual introduction of "industrially fractured" connecting rods.
Distinguishing features:
A. Older type connecting rods (smooth joint along contact surface)
B. Industrially fractured connecting rods (rough joint along contact surface)
Older type connecting rods
1. Piston rings
^ Offset gaps by 120°
^ Use piston ring pliers to remove and install
^ "TOP" faces piston crown
^ Checking ring gap
^ 2-part oil scraper ring
2. Piston
^ Checking; Refer to Fig 3
^ Mark installation position and cylinder number
^ Arrow on piston crown points to belt pulley end
^ Checking ring to groove clearance
^ Install using piston ring clamp
3. Connecting rod
^ Only replace as a set
^ Mark allocation to cylinder -B
^ Installation position: Marking -A- faces belt pulley end
4. Connecting rod bearing cap
^ Mark allocation to cylinder -B
^ Installation position: Marking -A- faces belt pulley end
5. 30 Nm + 1/4 turn (90°) further
^ Replace
^ Oil thread and contact surface
^ To measure radial clearance tighten to 30 Nm, but do not turn further
6. Bearing shell
^ Observe installing position
^ Do not interchange used bearing shells
^ Ensure retaining lugs fit tightly in recesses
^ Upper bearing shell with oil drilling for piston pin lubrication
^ Axial clearance, new: 0.05...0.31 mm; Wear limit: 0.37 mm
^ Check radial clearance with Plastigage, new: 0.01...0.06 mm; Wear limit: 0.12 mm
^ Do not rotate crankshaft when checking radial clearance
7. Cylinder block
8. Connecting rod bolt
9. Circlip
10. Piston pin
^ If difficult to remove, heat piston to 60°C
^ Remove and install with VW222a
Industrially fractured connecting rods
1. Piston rings
^ Offset gaps by 120°
^ Use piston ring pliers to remove and install
^ "TOP" faces piston crown
^ Checking ring gap
^ Checking ring to groove clearance
^ Oil scraper ring 2- or 3-part
2. 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
3. Floating piston pin If difficult to remove, heat piston to 60°C Remove and install with VW222A
4. Snap ring
5. Connecting rod
^ With cracked bearing cap
^ Only replace as a set
^ Mark relationship to cylinder-B
^ Installation position: Marking -A- faces belt pulley end
6. Bearing shell
^ Observe installation position
^ Insert bearing shells centrally
^ Do not interchange used bearing shells
^ Check if seated securely
^ Axial clearance, new: 0.10...0 35 mm; Wear limit: 0.4 mm
^ Check radial clearance with Plastigage, new: 0.01...0.05 mm; Wear limit: 0.09 mm
^ Do not rotate crankshaft when checking radial clearance
7. Cylinder block
^ Checking cylinder bore; Refer to Fig 5
^ Piston and cylinder dimensions; Refer to Cylinder Block; Specifications
8. Connecting rod bearing cap
^ Observe installing position
^ Caps only fit in one position and only on appropriate connecting rod due to breaking procedure (industrially fracturing) separating cap from connecting rod
9. 30 Nm + 1/4 turn (90°) further
^ Torx E10
^ Replace
^ Oil thread and contact surface
^ To measure radial clearance tighten to 30 Nm, but do not turn further
Fig. 1 Checking piston ring gap
Special tools, testers, measuring instruments and auxiliary items required
^ Feeler gauge
Work sequence
^ Push ring squarely from above down to approximately 15 mm from bottom end of cylinder.
Fig. 2 Checking ring to groove clearance
Special tools, testers, measuring instruments and auxiliary items required
^ Feeler gauge
Work sequence
Clean groove before checking.
Fig. 3 Checking piston
Special tools, testers, measuring instruments and auxiliary items required
^ External micrometer 75...100 mm
Work sequence
^ Measure pistons approximately 10 mm from the lower edge of skirt, 90° offset to axis of floating piston pin.
Deviation from nominal dimension: max. 0.04 mm
Fig. 4 Installation position of bearing shells
Bearing shell -1- with oil channel (arrow) for connecting rod
Bearing shell -2- without oil channel connecting rod bearing cap
^ Insert bearing shells and connecting rod bearing cap centrally.
Dimension -a- must be same on both left and right side, maximum deviation 0.2 mm
Fig. 5 Checking cylinder bores
Note: Measuring the cylinder bores must not be done when the cylinder block is mounted on a repair stand with adapter bracket VW540, as incorrect measurements would then be possible.
Special tools, testers, measuring instruments and auxiliary items required
^ Internal dial gauge 50...100 mm
^ Measure bores at 3 locations in both directions -A- across engine and -B- in line with crankshaft.
Deviation from nominal dimension: max. 0.08 mm
Piston and Cylinder Dimensions