Piston: Service and Repair
Piston and Connecting Rod Overview
1 Bolt
• 45 Nm + 90° (1/4) additional turn.
• Always replace.
• Use the old bolts to measure the radial play.
• Do not turn the additional 90° (1/4) turn when measuring the radial play.
• Lubricate the threads and contact surface.
2 Connecting Rod Bearing Cap
• Pay attention to the installed position.
• Mark the affiliation to the cylinder - A -.
• Installed position: The marks - B - point to the belt pulley side.
• Due to the way the separated connecting rod breaks (cracks), the cap fits only in one position and only onto the respective connecting rod.
• Separating a new connecting rod. Refer to => [ New Connecting Rod Separating ] Procedures.
3 Bearing Shells
• Note the installed position, refer to => [ Bearing Shell, Installed Position ].
• Do not interchange used bearing shells (mark them).
• Axial play:
New: 0.10 to 0.35 mm
Wear limit: 0.4 mm
• Measure radial clearance using Plastigage.
New: 0.020 to 0.060 mm
Wear limit: 0.090 mm
Do not rotate the crankshaft when measuring the radial play.
4 Pressure Relief Valve
27 Nm
• Opening pressure 1.6 to 1.9 bar.
5 Oil Spray Jet
• For piston cooling.
• See notes in => [ If metal shavings or a large quantity of small metal particles are found when repairing an engine, this could indicate that the crankshaft or connecting rod bearings are damaged. To prevent further damage, perform the following steps after the repair: ] Oil Pan and Oil Pump.
6 Circlip
7 Piston Pin
• If difficult to move, heat the piston to approximately 60 °C (140 °F).
• Remove and install using the pilot drift (VW 222 A).
8 Piston
• Mark the installed position and cylinder allocation.
• The arrow on the piston face points toward the belt pulley side.
• Install using a piston ring compressor.
• Checking, refer to => [ Pistons, Checking ].
• Checking the cylinder bore, refer to => [ Cylinder Bore, Checking ].
• For the correct piston and cylinder dimensions, refer to => [ Piston and Cylinder Dimensions ] Piston and Cylinder Dimensions.
9 Compression Ring
• Offset gaps by 120°
• Use piston ring pliers for removal and installation.
• The "TOP" mark must face up toward the piston crown.
• Checking the ring gap, refer to => [ Piston Ring Gap, Checking ].
• Checking the piston ring groove clearance, refer to => [ Piston Ring Groove Clearance, Checking ].
10 Oil Scraping Ring
• 2 pieces.
• Install the upper steel ring so the gap is offset by 120° to the neighboring compression ring.
• Offset all oil scraping ring component gaps to each other.
• Checking the ring gap, refer to => [ Piston Ring Gap, Checking ].
• The side clearance cannot be measured.
11 Connecting Rod
• Only replace as a set.
• Mark the affiliation to the cylinder - A -.
• Installed position: The marks - B - point to the belt pulley side.
• Separating a new connecting rod, refer to => [ New Connecting Rod Separating ] Procedures.
Piston Ring Gap, Checking
Special tools, testers and auxiliary items required
• Feeler Gauge
Test Sequence:
- 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
Special tools, testers and auxiliary items required
• Feeler Gauge
Test Sequence:
- Clean the ring groove in the piston before checking.
Pistons, Checking
Special tools, testers and auxiliary items required
• Micrometer 75-100 mm (VAS 6071)
Test Sequence:
- Measure the piston approximately 10 mm from the bottom edge and at points offset 90° to the piston pin axis.
• Deviation from nominal dimension: Max. 0.04 mm.
Cylinder Bore, Checking
Special tools, testers and auxiliary items required
• Cylinder Gauge (VAS 6078)
Do not bore, hone, grind or rework the cylinder bores with workshop tools. Reworking damages the surface of the cylinder bore.
Test Sequence:
- Measure diagonally at 3 positions transversely - A - and longitudinally - B -.
• Deviations from nominal dimension: Max. 0.08 mm
• Measurement of the cylinder bore may not be performed when the cylinder block is mounted on the engine and transmission holder (VAS 6095) , incorrect measurements are possible.
Bearing Shell, Installed Position
- Place the bearing shells centrally into the connecting rod and connecting rod cap.
• Dimension - a - must be the same on the left and right sides.