Piston: Service and Repair

Pistons and Connecting Rod Overview






1 Piston Rings

• Offset gaps by 120°

• Use piston ring pliers for removal and installation.

• "TOP" faces toward piston crown.

• Checking ring gap, refer to => [ Piston Ring Gap, Checking ].

• Checking piston ring groove clearance, refer to => [ Piston Ring Groove Clearance, Checking ].

2 Piston

• With the combustion chamber.

• Mark the installed position and cylinder allocation.

• Installed position and allocation, piston/cylinder. Refer to => [ Installed Position of the Piston and Piston/Cylinder Allocation ].

• Arrow on the piston face points toward the belt pulley side.

• Install with a piston ring compressor.

• Replace if the piston skirt is cracked.

• Checking the piston projection in Top Dead Center (TDC), refer to => [ Piston Projection in TDC, Checking ] Testing and Inspection.

3 Piston Pin

• If difficult to move, heat the piston to 60 °C (140 °F).

• Remove and install using the pilot drift (VW 222).

4 Circlip

5 Connecting Rod

• Mark the allocation to the cylinder using a colored mark - A -.

• Installed position: the marks - B - face the belt pulley side.

• With a cracked bearing cap.

• Separating new connecting rods, refer to => [ New Connecting Rod, Separating ] Procedures.

6 Bearing Shell

• Note the installed position, refer to => [ Bearing Shells, Installed Location ] Bearing Shells, Installed Location.

• Pay attention to the version: upper bearing shell (facing the piston) is made from wear resistant material; how to recognize it: a black line on the running surface near the separating point.

• Do not interchange used bearing shells.

• Insert bearing shells in the center.

• Ensure the bearing shell is seated tightly.

• Axial play:

Wear limit 0.37 mm

• Measure the radial play using Plastigage(R):

Wear limit: 0.08 mm

• Do not rotate the crankshaft when measuring radial play.

7 Cylinder Block

• Checking, cylinder bore. Refer to => [ Cylinder Bore, Checking ].

• Piston and cylinder dimensions. Refer to => [ Piston and Cylinder Dimensions ] [1][2]Specifications.

8 Connecting Rod Bearing Cap

• Note the installed position.

• Due to the separation procedure (cracking) of the connecting rod, the connecting rod bearing cap only fits in one position and only to the corresponding connecting rod.

9 Oil Spray Jet

• For piston cooling.

10 Bolt with Pressure Relief Valve

• 27 Nm

• Install without sealant.

11 Bolt

• 30 Nm + an additional 90° (1/4) turn.

• Always replace.

• Lubricate the threads and contact surface.

• Use a old bolt to measure radial play.

Piston Ring Gap, Checking





Special tools, testers and auxiliary items required

• Feeler Gauge

Procedure

- Push the piston ring squarely from above down to approximately 15 mm from the bottom end of the cylinder.






Piston Ring Groove Clearance, Checking





Special tools, testers and auxiliary items required

• Feeler Gauge

Procedure

- Before measuring, clean the ring groove.






Cylinder Bore, Checking





Special tools, testers and auxiliary items required

• Inside Caliper 50-100 mm

Procedure

- Measure the bore at 3 locations in both directions - A - across the engine and - B - in line with the crankshaft.

• Deviations to the nominal size: maximum 0.10 mm

• The cylinder bore must not be measured when the cylinder block is mounted on the engine and transmission holder (VAS 6095) because the measurements may be incorrect.

Installed Position of the Piston and Piston/Cylinder Allocation





The arrow on the piston crown - arrows - faces toward the belt pulley side.