Cylinder Block Assembly: Service and Repair

Pistons and connecting rods, disassembling and assembling





1. Piston rings
^ Offset ring gaps by 120°
^ Position oil scraper ring gap in tight winded spring area
^ Use piston ring pliers to remove and install
^ "TOP" faces toward piston crown
^ Checking ring gap
^ Checking ring to groove clearance
2. Piston
^ With combustion chamber
^ Mark installation position and cylinder number.
^ Mark installation position and application piston/cylinder
^ Arrow on piston crown points to belt pulley end.
^ Install using piston ring clamp.
^ Cracks on piston skirt, replace piston
^ Checking piston projection at TDC
3. Piston pin
^ If difficult to remove heat piston to 60°C
^ Remove and install with drift VW222a
4. Circlip
5. Connecting rod
^ Mark cylinder number -A- with colored pen
^ Installed position: Marking -B- faces pulley end
^ With industrially cracked bearing caps.
6. Bearing shell
^ Note installed position
^ Note versions:
^ Upper bearing shell (to piston) made out of more hard-wearing material
^ Distinguishing features: Black line on contact surface in separating area
^ Do not interchange used bearing shells.
^ Insert bearing shells centrally
^ Check for secure seating
^ Axial clearance. Wear limit: 0.37 mm
^ Check radial clearance with Plastigage, Wear limit: 0.08 mm
^ Do not rotate crankshaft when checking radial clearance
7. Cylinder block
^ Checking cylinder bores; Refer to Fig. 3
8. Connecting rod bearing cap
^ Note installed position.
^ Caps only install in one position and only on appropriate connecting rod due to breaking procedure (industrially cracking) separating cap from connecting rod
9. Oil spray jet
^ For piston cooling.
10. 25 Nm
^ Insert without sealant
11. Connecting rod bolt, 30 Nm plus an additional 1/4 turn (90°)
^ Always replace
^ Oil threads and contact surfaces.
^ To measure radial clearance use old bolts





Fig. 1 Checking piston ring gap

Special tools and equipment
^ Feeler gauges

^ Push ring down squarely from above to approximately 15 mm from bottom end of cylinder.





^ Determine ring gap with feeler gauge.





Fig. 2 Checking ring to groove clearance

Special tools and equipment
^ Feeler gauges

^ Clean ring groove before checking.





^ Determine clearance with feeler gauge.





Fig. 3 Cylinder bores, checking

Special tools and equipment
^ Internal dial gauge 50 to 100 mm
^ Take measurements at 3 positions in both lateral -A- and longitudinal -B- planes, as illustrated. Deviation from nominal dimension max. 0.10 mm

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 be possible.





Fig. 4 Piston installed position and piston/cylinder application
Piston in cylinders 1 and 2:
Larger intake valve chamber toward flywheel (arrows)
Piston in cylinders 3 and 4:
Larger intake valve chamber toward belt pulley side (arrows).

Note: New piston/cylinder allocations are shown by a colored marking on the piston crown.

^ Piston for cylinder 1 and 2: marked 1/2
^ Piston for cylinder 3 and 4: marked 3/4





Fig. 5 Installed position of bearing shells
Center bearing shells when inserting into connecting rod and connecting rod bearing cap.
Dimension -a- must be equal on both left and right sides
Max. deviation: 0.2 mm