Procedures

Pistons & Connecting Rods, Disassembly & Assembly






Note:

- A serrated Conrod was put into floating use from model year 1998.
- The serrated Conrod uses M8 and M8.5 bolts. Always measure the thread as different tightening torques apply. Incorrect tightening could result in engine damage.

1. Conrod bolt
- M8: 30 Nm + 1/4 turn (90°)
- M8.5: 40 Nm + 1/4 turn (90°)
- Always replace
- Oil threads and contact surface
- To measure radial clearance tighten to 30 Nm but not further
2. Conrod bearing cap
- Mark conrods to identify which cylinder they belong to, -A
- Mounting position: Markings -B indicate Cyls. 1-3 to pulley side, Cyls. 4-6 to flywheel side
3. Bearing shell
- Observe mounting position
- Do not exchange used bearing shells
- Measure radial play with plastigage:
- New: 0.015. - 0.062 mm
- Wear limit: 0.120 mm
- Do not turn crankshaft during radial play measurement
4. Conrod
- Only replace as a complete set
- Mark conrods to identify which cylinder they belong to, -A
- Installation position Mark -B- indicates: Cyls. 1-3 to belt pulley side, Cyls. 46 to flywheel side
5. Circlip
6. Piston pin
- If difficult to remove, heat piston to 60° C
7. Piston
- Mark mounting position and cylinder match
- Arrow on bottom of piston points to pulley side
- Use piston ring tensioning strap to install
- Checking see Fig. 4
- Check cylinder bore see Fig. 5
- Force feed oil nozzle for piston cooling
8. Piston ring
- Offset gaps by 120°
- Remove and install with piston ring pliers
- "TOP" faces toward piston crown
- Checking ring gap see Fig. 1
- Checking ring to groove clearance see Fig. 2.

Fig. 1 Checking piston ring gap








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

Fig. 2 Checking ring to groove clearance








Clean groove before check.

Fig. 3 Checking piston
Special tools and equipment





- Micrometer 75 - 100 mm
- Measure approximately 10 mm from lower edge and offset 90° to piston pin axis. Deviations from nominal dimensions max. 0.04 mm.
Nominal dimension; Piston and cylinder dimensions

Fig. 4 Checking cylinder bores
Special tools and equipment





- Internal dial gauge 50 - 100 mm
- Take measurements at 3 positions in both lateral -A- and longitudinal -B- directions, as illustrated. Deviation from nominal dimension max. 0.08 mm.

Note: Measuring the cylinder bores must not be done when the cylinder block is mounted on a repair stand with adapter bracket VW 540, as incorrect measurements would then be possible.

Fig. 5 Serrated conrods from model year 1998





Identifying features:
A- Conventional conrods (smooth separation surface)
B - Serrated conrods (rough separation surface)

Piston and cylinder dimensions