Connecting Rod: Service and Repair

Pistons and connecting rods, disassembling and assembling

Note: Mount in engine stand VW 540 before beginning work.

1. Piston ring
^ Offset gaps by 120°
^ Remove and install using piston ring pliers
^ "TOP" faces towards piston crown
^ Ring gap, checking, Refer to Fig. 1
^ Ring to groove clearance checking, Refer to Fig. 2
^ 2-part oil scraper ring
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. Connecting rod
^ Only replace as a set
^ Mark cylinder number -B
^ Installation position: Marking -A- faces towards pulley end
4. Connecting rod bolt
^ For Engine Code AEG
^ Always replace
5. Connecting rod bearing cap
^ Mark cylinder number -B
^ Installation position: Marking -A- faces towards pulley end
6. 30 Nm (22 ft. lbs.) plus additional 903 (1/4 turn)
^ Only Engine Code AEG
^ Always replace
^ Oil threads and contact surfaces
^ To measure radial clearance tighten to 30 Nm (22 ft. lbs.) but no further
^ 90° additional angle can be measured with torque angle meter i.e., Hazet 6690
7. Conrod bolt 30 Nm (22 ft. lbs.) plus additional 90° (1/4 turn)
^ For Engine Codes AVH, AZG
^ Always replace
^ Oil threads and contact surfaces
^ To measure radial clearance tighten to 30 Nm (22 ft. lbs.) but no further
^ 90° additional angle can be measured with torque angle meter i.e., Hazet 6690
8. Pressure relief valve
^ 27 Nm (20 ft. lbs.)
^ Opening pressure: 2.5 to 3.2 bar (36 to 46 psi)
9. Oil spray jet
^ For piston cooling
10. Bearing shell
^ Note installation position
^ Do not interchange used bearing shells
^ Insert bearing shells centrally
^ Ensure retaining lugs fit tightly in recesses
Axial clearance
^ New: 0.05 0.35 mm
^ Wear limit: 0.40 mm
Check radial clearance with Plastigage:
^ New: 0.01 0.06mm
^ Wear limit: 0.12 mm
^ Do not rotate crankshaft when checking radial clearance
11. Engine block
^ Checking cylinder bores, Refer to Fig. 4
^ Piston and cylinder dimensions, Refer to Piston, Engine, Specifications, Mechanical
12. Circlip
13. Piston pin
^ If difficult to remove, heat piston to 60°C (140°F)
^ Remove and install using VW 222a





Fig. 1 Piston ring gap, checking
Special tools and equipment
^ Feeler gauges





- Push piston ring squarely from above down to approximately 15 mm from bottom end of cylinder bore.





Fig. 2 Ring to groove clearance, checking
Special tools and equipment
^ Feeler gauges





Clean groove before check.





Fig. 3 Piston, checking
Special tools, test equipment and auxiliary items
^ Micrometer 75 to 100 mm (2.95 to 3.95 inch)

- Measure pistons approximately 10 mm from lower edge of skirt, at 90^angle to piston pin axis.
^ Deviation from nominal dimension max. 0.04 mm





Fig. 4 Cylinder bores, checking
Special tools and equipment
^ Internal dial gauge 50 to 100 mm (2.95 to 3.95 inch)
- Measure bore at 3 locations in both directions -A- across engine and -B- in line with crankshaft.
^ Deviation from nominal dimension max. 0.08 mm

Note: Do NOT measure the cylinder bores when the engine block is mounted on a repair stand using the VW 540 adapter bracket, inaccurate measurements will result due to the uneven bending of the engine block on the repair stand.