Piston: Service and Repair
Pistons and Connecting Rod Overview
1 Bolt
• M8 bolt - 30 Nm + 90 degrees (1/4) additional turn.
• M9 bolt - 45 Nm + 90 degrees (1/4) additional turn.
• Always replace
• Lubricate the threads and contact surface.
• Use the old bolts to measure the radial play.
• Do not tighten the additional 90 degrees when measuring the radial play.
2 Connecting Rod Bearing Cap
• Note the installed position.
• Due to the separation procedure (cracking) for the connecting rod, the cap only fits in one position and only on the correct connecting rod.
• Mark the affiliation to the cylinder - A -
• Installed position: the marks - B - face the belt pulley side.
3 Bearing Shells
• Installed location, refer to => [ Installed Position of the Bearing Shell ].
• Do not interchange used bearing shells (mark them).
• Axial play new: 0.10 to 0.35 mm, wear limit: 0.40 mm.
• Check radial clearance using Plastigage, new: 0.02 to 00.06 mm, wear limit: 0.09 mm Do not rotate the crankshaft when checking the radial clearance.
4 Pressure Relief Valve
• 27 Nm
• Opening pressure: 1.6 to 1.9 bar
5 Oil Spray Jet
• For piston cooling.
6 Circlip
7 Piston Pin
• If the piston is difficult to move, heat the pin to 60 degrees C (140 degrees F).
• Remove and install using pilot drift (VW 222 A).
8 Piston
• Checking, refer to.
• 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.
• Piston and cylinder dimensions. Refer to => [ Piston and Cylinder Dimensions ] Piston and Cylinder Dimensions.
• Cylinder bore, checking.
9 Compression Rings
• Offset gaps by 120 degrees
• Use piston ring pliers for removal and installation.
• "TOP" mark must face up toward the piston crown.
• Checking ring gap, refer to => [ Piston Ring Gap, Checking ].
• Checking piston ring groove clearance, refer to => [ Piston Ring Groove Clearance, Checking ].
10 Oil Scraping Ring
• 2 piece
• Install the upper steel ring so the gap is offset by 120 degrees to the neighboring compression ring.
• Offset the oil scraping ring gaps to each other.
• Checking ring gap, refer to => [ Piston Ring Gap, Checking ].
• Side clearance cannot be measured.
11 Connecting Rod
• Only replace as a set.
• Mark affiliation to the cylinder - A -.
• Installed position: the marks - B - face the belt pulley side.
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
Special tools, testers and auxiliary items required
• Micrometer 75-100 mm (VAS 6071)
- Measure the pistons approximately 10 mm from the bottom edge and at points offset by 90 degrees 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.
- Measure diagonally at 3 positions transversely - A - and longitudinally - B -.
• Deviation 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), false measurements are possible.
Installed Position of the Bearing Shell
- Place the bearing shell centrally into the connecting rod and connecting rod bearing cap.
Dimension - a - must be the same on the left and right sides.