Connecting Rod: Description and Operation
Pistons and Connecting Rod Overview
• Oil spray jet for piston cooling.
1 Bolt
• 30 Nm + 90° (1/4) additional turn.
• Replace
• Lubricate the threads and contact surface.
• Tighten to 30 Nm to measure radial play, do not tighten further.
• Radial clearance, measuring. Refer to => [ Connecting Rod Radial Clearance, Checking ] Testing and Inspection.
2 Connecting Rod Bearing Cap
• Do not interchange.
• Affiliation to the cylinder mark - B -.
• Installed position: casting marks - A -.
3 Bearing Shells
• Note the installed position.
• Do not interchange used bearing shells (mark them).
• Bearing shells that are worn down to the nickel layer must be replaced.
• Radial clearance, measuring. Refer to => [ Connecting Rod Radial Clearance, Checking ] Testing and Inspection.
• When measuring radial clearance, tighten bolts - item 1 - to 30 Nm but do not tighten further.
4 Connecting Rod
• Only replace as set with the cap.
• Affiliation to the cylinder mark - B -.
• Installed position: casting marks - A -.
• Axial play for each new connecting rod and cap pair: 0.20 to 0.44 mm
5 Circlip
6 Piston Pin
• If tight, heat the piston to 60 °C (140 °F).
• Remove and install using a pilot drift (VW 222 A).
7 Piston
• With the combustion chamber.
• Mark the installed position and cylinder allocation.
• Checking.
• Install with a piston ring compressor.
• Replace if there are cracks on the piston shaft.
• Piston and cylinder dimensions. Refer to => [ Piston and Cylinder Dimensions ] [1][2]Specifications.
• Piston projection in Top Dead Center (TDC), checking. Refer to => [ Piston Projection in Top Dead Center, Checking ] Testing and Inspection.
• Cylinder bore, checking.
8 Piston Rings
• Offset the gaps by 120°
• Use piston ring pliers for removal and installation.
• The mark "TOP" must face toward the piston head.
• Checking ring gap.
• Checking piston ring groove clearance.
Oil Spray Jet for Piston Cooling
1. Bolt - 9 Nm
2. Oil spray jet for cooling the piston and spray jet valve
• 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 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
- Using an internal dial gauge 50 to 100 mm, 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: arrow - 1 - on the piston head points toward the belt pulley side.
• Mark the installed position and assignment to the cylinder on the piston crown of used pistons with chalk or a waterproof felt tip pen 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 before removing - arrow -.
• Only replace the connecting rod and cap as a set.
• Do not interchange 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.