Piston: Service and Repair

Pistons and Connecting Rod Assembly 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 ]

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

2 Piston

• With combustion chamber

• Mark installed position and cylinder allocation

• Installed position and allocation, piston/cylinder, refer to --> [ Installed Position of Piston and Piston/Cylinder Allocation ]

• Arrow on piston face points toward belt pulley side

• Install with piston ring compressor

• Replace if piston skirt is cracked

• Checking piston position at TDC, refer to --> [ Piston Projection in TDC, Checking ] Testing and Inspection.

3 Piston Pin

• If difficult to move, heat piston to 60 °C

• Removing and installing using a drift (VW 222)

4 Circlip

5 Connecting Rod

• Mark allocation to cylinder using a color marker - A -

• Installation position: Markings - B - point to belt pulley side

• With cracked bearing cap

• Separating new connecting rod, refer to --> [ New Connecting Rod, Separating ] Procedures.

6 Bearing Shell

• Note installation position. Refer to --> [ Bearing Shells, Installation Location ] Service and Repair.

• Note version: Upper bearing shell (to piston) made of wear-resistant material, identification: Black line on contact surface in area of separating point

• Do not interchange used bearing shells

• Insert bearing shells in center

• Ensure seated tightly

• Axial play wear limit: 0.37 mm

• Measure radial clearance with Plastigage: Wear limit: 0.08 mm

• Do not turn crankshaft when measuring radial play

7 Cylinder Block

• Cylinder bore checking, refer to --> [ Cylinder Bore, Checking ]

• Piston and cylinder dimensions, refer to --> [ Piston and Cylinder Dimensions ] [1][2]Specifications.

8 Connecting Rod Bearing Cap

• Note installation position

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

9 Oil Spray Jet

• Follow the Safety Precautions. Refer to --> [ If metal shavings or a large quantity of small metal particles are found when repairing an engine, this could indicate that the crankshaft and connecting rod bearings are damaged. To prevent further damage, perform the following steps after the repair: ] Service and Repair

• For piston cooling

• Oil spray jet and pressure relief valve, refer to --> [ Oil Spray Jet and Pressure Relief Valve ] Oil Pump, Oil Pan and Balance Shaft Module

10 Bolt with Pressure Relief Valve, 27 Nm

• Install without sealant

• Oil spray jet and pressure relief valve --> [ Oil Spray Jet and Pressure Relief Valve ] Oil Pump, Oil Pan and Balance Shaft Module

11 Connecting Rod Bolt, 30 Nm plus an additional 1/ 4 turn (90°)

• Replace

• Lubricate threads and contact surface

• Use old bolt to measure radial play

Piston Ring Gap, Checking





Special tools, testers and auxiliary items required

• Feeler gauge

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





Piston Ring Groove Clearance, Checking





Special tools, testers and auxiliary items required

• Feeler gauge

- Before measuring, clean ring groove.





Cylinder Bore, Checking





Special tools, testers and auxiliary items required

• Inside caliper 50 to 100 mm

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

• Deviations from nominal dimension: max. 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 Piston and Piston/Cylinder Allocation





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