Connecting Rod: Service and Repair
Pistons and Connecting Rod Overview
• Oil all bearing and contact surfaces before assembly work.
• Oil spray jet for piston cooling, refer to => [ Oil Spray Jet, for Piston Cooling ].
1 Bolt
• 30 Nm + an additional 90° (1/4) turn.
• Always replace.
• Lubricate the threads and contact surface.
• Tighten to 30 Nm to check the radial play, do not tighten the additional angle.
• Checking the radial clearance. Refer to => [ Connecting Rod Radial Clearance, Checking ] Testing and Inspection.
2 Connecting Rod Bearing Cap
• Do not interchange.
• Mark the cap to the rod - B -, to identify where it belongs. Refer to => [ Connecting Rod, Marking ].
• Installed position: Note the casting marks - A -.
3 Bearing Shells
• Pay attention to the installed position.
• Do not interchange used bearing shells (mark them).
• Bearing shells that are worn down to the nickel layer must be replaced.
• Checking the radial clearance. Refer to => [ Connecting Rod Radial Clearance, Checking ] Testing and Inspection.
• When checking the radial clearance, tighten the bolts - item 1 - to 30 Nm but do not tighten the additional torque angle.
4 Connecting Rod
• Always replace as a set.
• Mark the cap to the rod - B -, to identify where it belongs. Refer to => [ Connecting Rod, Marking ].
• Installed position: Note the casting marks - A -.
• Axial play for each new connecting rod pair:
0.20 to 0.44 mm
5 Lock Ring
6 Piston Pin
• If tight, heat the piston to 60 °C (140 °F).
• Remove and install using the pilot drift (VW 222 A).
7 Piston
• With a combustion chamber.
• Mark the installed position and cylinder allocation. Refer to => [ Piston Installed Position ].
• Checking, refer to => [ Piston, Checking ].
• Install using a piston ring compressor.
• Replace if there are cracks on the piston pin shaft.
• For the correct piston and cylinder dimensions, refer to => [ Piston and Cylinder Dimensions ] [1][2]Specifications.
• Checking piston projection in Top Dead Center (TDC). Refer to => [ Piston Projection in TDC, Checking ] Testing and Inspection.
• Checking the cylinder bore. Refer to => [ Cylinder Bore, Checking ].
8 Piston Rings
• Offset gaps by 120°.
• Use piston ring pliers for removal and installation.
• The word "TOP" must face toward the piston head.
• Checking the piston ring gap. Refer to => [ Piston Ring Gap, Checking ].
• Checking the piston ring groove clearance. Refer to => [ Piston Ring Groove Clearance, Checking ].
Oil Spray Jet, for Piston Cooling
1. Bolt - 9 Nm
2. Oil spray jet for cooling the piston and spray jet
• Opening pressure: 1.3 bar.
Piston Ring Gap, Checking
- Push the ring squarely, from above down to approximately 15 mm from the bottom end of the cylinder. To do this use a piston without rings.
Piston Ring Groove Clearance, Checking
- Clean the ring groove of the piston before checking.
Piston, Checking
- Measure approximately 10 mm from the lower edge at a 90° angle to the piston pin axis using an external micrometer (75 to 100 mm).
• Maximum deviation from nominal dimension: 0.05 mm.
Nominal dimension, refer to => [ Piston and Cylinder Dimensions ] [1][2]Specifications.
Cylinder Bore, Checking
- Use an internal dial gauge (50 to 100 mm), to measure at 3 points in a diagonal sequence horizontally - A - and vertically - B -.
• Maximum deviation from nominal dimension: 0.08 mm.
Nominal dimension, refer to => [ Piston and Cylinder Dimensions ] [1][2]Specifications.
Piston Installed Position
• Installed position: The arrow - item 1 - on the piston crown faces the belt pulley side.
• Mark the installed position and cylinder on the piston crown of used pistons with chalk or a waterproof marker so they can be reinstalled again.
• Do not use a center punch or scribe, since the piston head coating will be damaged.
Connecting Rod, Marking
- Mark the connecting rod and connecting rod bearing cap in relation to each other - arrow - before removing.
• Only replace the connecting rod and cap as a set.
• Do not interchange the connecting rod bearings.
Connecting Rod, Installed Position
The larger thrust flange on the connecting rod - arrow - faces the adjacent crankshaft bearing.
• The illustration shows the front connecting rod pair.