Pistons and Connecting Rods, Component Overview
Pistons and connecting rods, component overview
1 - Connecting rod bolt, 30 Nm + 90 degrees (1/4 turn) further
^ Replace
^ Lubricate threads and contact surface
^ To measure radial clearance, tighten to 30 Nm but not further
2 - Connecting rod bearing cap
^ Mark cylinder allocation -B-
^ Installed position: Markings -A- must be on same side
3 - Bearing shells
^ Installed position: retaining tabs of both bearing shells lie on same side of connecting rod
^ Do not interchange used bearing shells (mark)
^ Retaining tabs on bearing shells must fit tightly in recesses
^ Axial clearance, New: 0.05... 0.31 mm; Wear limit: 0.40 mm
^ Measure radial clearance with Plastigage
^ Do not rotate crankshaft when measuring radial clearance
^ Radial clearance, New: 0.02... 0.07 mm; Wear limit: 0.10 mm
^ Replacement parts are color coded "yellow" for lower and "red" for upper
4 - Connecting rod
^ With hole for piston pin lubrication
^ Only replace as a set
^ Mark cylinder allocation -B-
^ Installed position: Mark -A- faces toward shallow side of piston (shallow side of piston crown faces cylinder block center)
5 - Circlip
6 - Piston pin
^ If difficult to move, heat piston to 60 degrees C
^ Remove and install using drift VW 222 A
7 - Piston
^ Mark installed position to connecting rod and cylinder allocation
^ Shallow side of piston crown faces center of cylinder block
^ Piston and cylinder dimensions
^ Install using T10147
8 - Piston rings
^ Compression rings
^ Offset gaps by 120 degrees
^ Remove and install using piston ring pliers
^ "TOP" must face toward piston crown
^ Checking ring gap
^ Checking ring to groove clearance
9 - Piston ring
^ Oil scraping ring
^ 3-part
^ Install upper steel ring so gap is offset by 120 degrees to neighboring compression ring
^ Offset all gaps of oil scraping ring components to each other
Checking piston ring gap
- Insert ring at right angle to cylinder wall from above and push down into lower cylinder opening approx. 15 mm from bottom of cylinder. To do so, use a piston without rings.
- Use a feeler gauge to measure.
Checking ring to groove clearance
- Clean groove in piston before checking clearance.
- Use a feeler gauge to measure.
Checking piston
- Measure approx. 6 mm from lower edge, perpendicular to piston pin axis. Use an external micrometer, 75... 100 mm, to measure.
^ Max. deviation from nominal dimension: 0.04 mm
Checking cylinder bore
- Make measurements at three positions diagonally in transverse direction -A- and in longitudinal direction -B-. Use a cylinder gauge, 50... 100 mm, to measure.
^ Max. deviation from nominal dimension: 0.08 mm
Installing piston with tool T10147
Note:
If a new installing tool (funnel) is used to install the pistons, first pass a piston (with oiled piston rings) twice through the tool and remove any resulting metal debris. Only then install the piston with the piston rings.
- Lubricate tool and push piston in by hand.
^ Flat side of piston crown must face projection on installing tool (arrow).
- Hold tool (with piston inserted) on upper edge and press piston in with both thumbs.
- Push piston in until it protrudes approx. 15 mm from lower edge of installing tool.
- Place piston in appropriate cylinder bore.
^ Projection on installing tool (arrow) must face center of cylinder block.
- Hold installing tool firmly against cylinder block and push in piston.