Piston: Service and Repair

Pistons and Connecting Rod Overview

• Oil injector jet for piston cooling.






1 Bolts

• 30 Nm plus an additional 90° turn

• Replace

• Lubricate the threads and contact surface

2 Connecting Rod Bearing Cap

• Mark for installation later

• Mark allocation to cylinder with paint - B -.

• Installation position: Note the casting marks - A -

3 Bearing Shells

• Pay attention to the installed position

• Mark used bearing shells for reinstallation but not on the running surface

• Replace the bearing shells worn down to the base layer

4 Connecting Rod

• Only replace as a set

• Mark allocation to cylinder with paint - B -.
.
• Axial play for each new connecting rod pair: 0.20 to 0.44 mm

• Radial clearance, measuring, refer to => [ Connecting Rod, Measuring Radial Clearance ] Testing and Inspection

5 Circlip

• Replace

6 Piston Pin

• Heat piston to 60 °C 140 °F) if it is difficult to move.

• Removing and installing using a pilot drift (VW 222 A)

7 Piston

• Mark the installation position and cylinder allocation.

• Replace the piston if there are cracks on the piston head or piston shaft
.
• Install with piston ring compressor

• For the correct piston and cylinder dimensions, refer to => [ Piston and Cylinder Dimensions ] [1][2]Piston, Engine
.
• Measure the piston projection at "TDC", refer to => [ Piston Projection, Measuring at TDC ] Testing and Inspection

8 Piston Rings

• Offset gaps by 120°

• Use piston ring pliers for removing and installing

• Mark "TOP" must face toward piston head
.
Oil Spray Jet For Piston Cooling





1. Bolt - 9 Nm

2. Oil spray jet for cooling the piston and spray jet valve


Measuring the Piston Ring Gap





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

- To do this use a piston without piston rings.






Measuring the Ring to Groove Clearance





- Clean the piston ring groove before checking.






Pistons, Checking





- Measure approximately 0.39 in 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: 0.05 mm.

Nominal dimension, refer to => [ Piston and Cylinder Dimensions ] [1][2]Piston, Engine.

Cylinder Bore, Checking





- 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 Location





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 crown with a punch, notch or similar object.

• Installation position: The arrow - 1 - on the piston crown faces the belt pulley side.

Mark Connecting Rod





- Mark the connecting rod and connector rod bearing caps to each other and to the cylinder - arrow - with paint for installation.

• Only replace the connecting rods as a set.

• Do not interchange the connecting rod bearing.

Installation Position, Connecting Rod





• Installation position: The larger thrust flange on the connecting rod - arrows - faces the adjacent crankshaft bearing.

• The front connecting rod pair is shown in the illustration.