Piston and Connecting Rod, Disassembling and Assembling
Piston and connecting rod, disassembling and assembling
1 - Piston rings
- Offset gaps by 120 °
- Remove and install with piston ring pliers
- "TOP" marking faces toward piston crown
- Checking ring gap See Fig. 1
- Checking side clearance See Fig. 2
2 - Piston
- Checking Fig. 3
- Mark installation position and relationship to cylinder
- Arrow on base of piston points toward pulley end
- Install with piston ring compressor
- Dimensions See Fig. 4
3 - Connecting rod
- Replace only as set
- Mark matching cylinder number -B-
- Installation position:
- marking -A- points toward pulley end
- With oil hole for piston pin lubrication
4 - Bearing cap
- Note installation position
5 - 30 Nm (22ft lb) plus 1/4- turn (90 °)
- Oil threads and contact surface
- Measuring radial clearance:
- tighten to 30 Nm (22 ft lb) but NOT additional 1/4- turn (90 °)
CAUTION!
- DO NOT turn crankshaft while measuring radial clearance.
6 - Pressure relief valve
- Tightening torque: 27 Nm (20 ft lb)
- Opening pressure:
- 2.5 - 3.2 bar (36- 46 psi)
- Not applicable 08.95 ->
7 - Oil spray nozzle
- For piston cooling
- Not applicable 08.95 ->
Note:
- The oil spray nozzles and pressure relief valves have been discontinued with production from August 1995.
8 - Bearing shell
- Note installation position
- Do not interchange worn bearing shells
- Ensure correct seat in holding tabs
- Axial clearance:
- New: 0.05 - 0.31 mm (0.0020 - 0.0122 in.)
- Wear limit: 0.37 mm (0.0146 in.)
- Measure radial clearance with Plastigage;
- New: 0.01 - 0.06 mm (0.0004- 0.0024)
- Wear limit: 0.12 mm (0.0047 in.)
- With oil hole toward piston pin
CAUTION!
- DO NOT turn crankshaft while measuring radial clearance.
9 - Cylinder block
- Checking cylinder bore See Fig. 5
10 - Connecting rod bolt
11 - Circlip
12 - Piston pin
- If difficult to move, warm piston to 60 ° C (140 ° F)
- Remove and install with VW222a
Fig. 1 Checking piston ring gap
- Squarely insert piston ring into cylinder from above, to approx. 15 mm (5/8 in.) from bottom of cylinder.
Fig. 2 Checking piston ring side clearance
- Clean ring groove before testing.
Fig. 3 Checking piston
- Measure approx. 10 mm (0.4 in.) from lower edge of piston skirt at right angle (90 °) to piston pin.
- Maximum deviation from nominal diameter; 0.04 mm (0.0016 in.)
Note:
- Only pistons and piston rings of the same type and pistons of the same weight class may be installed.
Fig. 4 Piston dimensions
Fig. 5 Checking cylinder bore
- Measure in direction -A- perpendicular to crankshaft, and direction -B- parallel to crankshaft.
- Measure at -1- 10 mm (0.039 in.) from top, -2- (center) and -3- 10 mm (0.039 in.) from bottom.
- Use 50-100 mm internal micrometer.
- Maximum deviation from nominal diameter; 0.08 mm (0.0015 in.)
CAUTION!
- DO NOT measure cylinder bore when cylinder block is mounted in VW540 holding fixture. Measurement accuracy can be affected by cylinder block distortion as it hangs down from the engine stand.
Piston and cylinder dimensions 07.95 1)
1) Flat top Piston with center combustion chamber recess
Piston and cylinder dimensions 08.95-07.96 1)
�6�:
1) Stepped piston crown with valve relief, installed in some m.y. 1996 vehicles.
2) Dimension stamped on piston crown. Add 0.015 mm (0.0006 in.) for actual diameter including phosphate layer.
Piston and cylinder dimensions 08.95 -> 1)
1) Flat top Piston with center combustion chamber recess