Pistons and Connecting Rods, Component Overview

Pistons and connecting rods, component overview

Note: Oil injector jet for piston cooling





1 - Connecting rod bolt, 30 Nm plus 1/4 turn (90°)
^ Replace
^ Lubricate threads and contact surface
^ Tighten to 30 Nm to measure radial play, do not turn further

2 - Connecting rod bearing cap
^ Do not interchange
^ Mark allocation to cylinder using a color marker - B -
^ When installing bearing cap, observe: The wide thrust flange - A - must point to the same side on connecting rod and connecting rod bearing cap
^ Installation position of connecting rod pairs

3 - Bearing shells
^ Check that retaining tabs are secured
^ Do not interchange used bearing shells (mark, but not on running surface)
^ Over-sized bearings are available for reworked crankshaft connecting rod journals

4 - Connecting rod
^ Only replace as set
^ Mark allocation to cylinder with paint - B -
^ When installing bearing cap, observe: The wide thrust flange - A - must point to same side on connecting rod and connecting rod bearing cap
^ Installation position of connecting rod pairs
^ Axial play for each new connecting rod pair: 0.20 to 0.38 mm
^ Axial play wear limit: 0.60 mm

5 - Piston pin
^ If tight, heat piston to 60°C
^ Removing and installing using a drift VW 222 A

6 - Circlip
7 - Piston
^ Installation position of pistons
^ checking
^ Install with piston ring compressor
^ Measuring cylinder bore

8 - Piston rings
^ Offset gaps by 120°
^ Use piston ring pliers for removal and installation
^ "TOP" marking or inscribed side must point to piston head
^ Measuring end cap





Measuring piston ring gap
- Insert ring at right angle to cylinder wall from above to lower cylinder opening approximately 15 mm from cylinder edge. When inserting, use piston without rings








Measuring piston ring side clearance
- Before measuring, clean piston ring groove.








Checking piston
- Measure approximately 10 mm from lower edge, at 90° angle to piston pin axis using an external micrometer of 75 to 100 mm.
^ Maximum deviation from nominal dimension: 0.04 mm
Nominal dimension





Measuring cylinder bore
- Using an internal dial gauge of 50 to 100 mm, measure at 3 points in diagonal sequence horizontally - A - and vertically - B -.
^ Maximum deviation from nominal dimension: 0.08 mm.
Nominal dimension





Piston installation position
- Mark allocation to cylinder on piston head using chalk or waterproof felt pen.

Note: Do not use a center punch or scribe, since the piston head coating will be damaged.

Installation position:
^ Arrows on piston heads point to belt pulley side.
^ Valve recesses - 1 - point toward center of engine.





Marking connecting rods

Note:
^ Replace the connecting rods only as a set.
^ Do not interchange the connecting rod bearings.

- Before removing, mark allocation of connecting rod and connecting rod bearing caps to each other and to cylinder using a color marker - arrow -.





Installed position of connecting rods

^ Molded tabs - arrows - at beveled surfaces of connecting rod pairs 1 and 2, 3 and 4, 5 and 6 as well as 7 and 8 must point toward each other.





Oil injector jet for piston cooling