Piston: Service and Repair
Pistons and Connecting Rod Overview
• Lubricate all bearings and running surfaces.
• Oil injector jet for piston cooling, refer to => [ Oil Spray Jet for Piston Cooling ].
1 Bolts
• Replace
• 50 Nm + 90° turn
• Lubricate the threads and contact surface
2 Connecting Rod Bearing Cap
• Mark for installation later
• Mark affiliation to cylinder with paint, refer to => [ Mark Connecting Rod ]
• Installation position of connecting rod pairs, refer to => [ Connecting Rod, Installed Location ]
3 Bearing Shells
• Check that retaining tabs are secured
• Replace any worn bearing shells
• Oversized bearings are available for reworked crankshaft connecting rod journal, refer to the Parts Catalog
• The connecting rod tabs are above each other
4 Connecting Rod
• Only replace as a set
• Mark affiliation to cylinder with paint, refer to => [ Mark Connecting Rod ]
• Installation position of connecting rod pairs, refer to => [ Connecting Rod, Installed Location ]
• Axial play for each new connecting rod pair: 0.20 to 0.45 mm
• Radial clearance, measuring, refer to => [ Connecting Rod, Measuring Radial Clearance ] Testing and Inspection
5 Circlip
• Replace
6 Piston Pin
• If tight, heat piston to 60 °C (140 °F)
• Removing and installing using a pilot drift (VW 222 A)
7 Piston
• Mark the installation position and cylinder allocation, refer to => [ Piston Installation Position ]
• Checking, refer to => [ Pistons, Checking ]
• Install with piston ring compressor
• Piston and cylinder dimensions, refer to => [ Piston and Cylinder Dimensions ] [1][2]Piston, Engine
• Measuring cylinder bore, refer to => [ Measuring Cylinder Bore ]
8 Piston Rings
• Offset gaps by 120°
• Use piston ring pliers for removing and installing
• Installation position: The "TOP" marking or side with writing faces the piston crown.
• Gap, measuring, refer to => [ Piston Ring End Gap, Measuring ]
• Measuring side clearance, refer to => [ Measuring Piston Ring Side Clearance ]
Piston Ring End Gap, Measuring
- Push the piston ring squarely from above down to approximately 15 mm from the bottom end of the cylinder.
- Use a piston without a piston ring for sliding in.
Measuring Piston Ring Side Clearance
- Clean the piston ring groove before checking.
Pistons, Checking
- Measure approximately 15 mm from the lower edge at a 90° angle to the piston pin axis using a 75 to 100 mm external micrometer.
• Maximum deviation from nominal dimension: 0.03 mm.
Nominal dimension, refer to => [ Piston and Cylinder Dimensions ] [1][2]Piston, Engine.
Measuring Cylinder Bore
- Measure in a diagonal sequence at 3 positions transversely - A - and longitudinally - B - using a cylinder gauge (VAS 6078) or inside micrometer set 18-100 mm (US1033/S).
• Maximum deviation from nominal dimension: 0.08 mm.
Nominal dimension, refer to => [ Piston and Cylinder Dimensions ] [1][2]Piston, Engine.
Piston Installation Position
The coating on the piston crown could be destroyed.
• Mark the allocation to the cylinder on the piston crown with paint to install used pistons. Do not mark the piston head with a punch, notch or something similar.
Installation position:
• The arrows on the piston heads point to the belt pulley side.
Mark Connecting Rod
• Only replace connecting rod as a set.
- Mark the connecting rod and connector rod bearing caps to each other and to the cylinder - arrow - with paint for installation.
Connecting Rod, Installed Location
• The molded tabs - arrows - on the beveled surfaces of the connecting rod pairs "1 and 2", "3 and 4" and "5 and 6" must face each other.
Oil Spray Jet for Piston Cooling
1. Insert the bolt with locking compound and tighten to 9 Nm; locking compound, refer to the Parts Catalog.
2. Oil spray jet with spray nozzle valve (opening pressure 2 to 2.4 bar (29 to 34.80 psi))
The oil spray jets could get damaged.
• Do not bend the oil injector jets.
• Bent oil injector jets must be replaced.