Connecting Rod: Service and Repair
Pistons and Connecting Rod Assembly Overview
1 Bolt
• Replace
• Lubricate threads and contact surface
• 30 Nm plus an additional 90° (1/4) turn.
• Use old bolts for radial play measurement, tighten to 30 Nm but do not tighten further
2 Connecting Rod Bearing Cap
• Affiliation to the cylinder mark - B -
• Installation position: Markings - A - must align
3 Bearing Shells
• Mark used bearing shells
• Bearing shell retaining tabs must be firmly seated in the notches
• Installation position: Retaining tabs of both bearing shells lie on the same side of the connecting rod
• Measuring axial play, refer to => [ Connecting Rod, Measuring Axial Clearance ] Testing and Inspection
• Radial clearance, measuring, refer to => [ Connecting Rod, Measuring Radial Clearance ] Connecting Rod, Measuring Radial Clearance
• Replacement parts are color coded "yellow" for lower and "red" for upper
4 Connecting Rod
• With oil hole for piston pin lubrication
• Only replace as set
• Affiliation to the cylinder mark - B -
• Installation position: - A - markings face toward lower side of piston crown (to center of cylinder block)
5 Circlip
6 Piston Pin
• If tight, heat piston to 60 °C / 140 °F
• Removing and installing using a drift (VW 222 A)
7 Piston
• Checking, refer to => [ Pistons, Checking ]
• Mark installed location to connecting rod and affiliation to cylinder
• Shallow side of piston head faces cylinder block center
• Piston and cylinder dimensions, refer to => [ Piston and Cylinder Dimensions ] [1][2]Piston, Engine
• Install using fitting tool (T10147), refer to => [ Installing Piston with ]
8 Piston Rings
• Compression rings
• Offset gaps by 120°
• Use piston ring pliers for removal and installation
• Mark "TOP" must face toward piston head
• Checking ring gap, refer to => [ Piston Ring Gap, Checking ]
• Check piston ring groove clearance, refer to => [ Ring to Groove Clearance, Checking ]
9 Piston Ring
• Oil scraping ring
• 3-part
• Install upper steel ring so gap is offset by 120° to neighboring compression ring
• Offset all oil scraping ring component gaps to each other
Piston Ring Gap, Checking
- Slide piston ring from above into lower cylinder opening as follows, using piston without piston ring.
• Right angle to cylinder wall.
• Until approximately 15 mm from bottom edge of cylinder.
- Measure with feeler gauge.
Ring to Groove Clearance, Checking
- Clean piston ring groove.
- Measure with feeler gauge.
Pistons, Checking
- Measure with external micrometer 75 to 100 mm as follows:
• Approximately 6 mm from bottom edge.
• Offset 90° to piston pin axle.
Deviation from nominal dimension:
• Maximum 0.04 mm.
Nominal dimension, refer to => [ Piston and Cylinder Dimensions ] [1][2]Piston, Engine.
Cylinder Bore, Checking
- Measure with internal dial gauge 50 to 100 mm as follows:
• Diagonally at 3 positions transversely - A - and longitudinally - B -.
Deviation from nominal dimension:
• Maximum 0.08 mm.
Nominal dimension, refer to => [ Piston and Cylinder Dimensions ] [1][2]Piston, Engine.
Installing Piston with Funnel (T10147)
• If a new Piston Insertion Funnel (T10147) is used, pistons must first be guided twice through the funnel with lubricated piston rings and any shavings resulting from this must be removed. Then the pistons can be installed with piston rings.
- Push piston by hand into oiled piston installation tool.
• Flat side of piston crown must face toward funnel pin - arrow -.
- Hold funnel (with piston inserted) on upper edge and press piston in with both thumbs.
- Push piston in until it protrudes approximately 15 mm from lower edge of funnel.
- Place pistons in appropriate cylinder bore.
• Funnel pin - arrow - must point toward center of cylinder block.
- Press funnel tightly against cylinder block and push piston in.