Piston: Service and Repair

Note: Support engine with VW 540 support before repairing.





1. Piston ring
^ Offset ring gaps 120°
^ Remove and install using piston ring pliers
^ "TOP" faces towards crown
^ Ring gap, checking see Fig. 1
^ Ring to groove clearance see Fig. 2
2. Piston
^ With combustion chamber
^ Mark installation position and cylinder number see Fig. 4
^ Arrow on piston crown points to pulley end
^ Install using piston ring tool
^ If piston skirt has cracks, replace piston
^ Piston projection at TDC, checking
3. Piston pin
^ If difficult to remove, heat piston to 60°C
^ Remove and install using VW 222A
4. Circlip
5. Connecting rod
^ Only replace as a set
^ Mark cylinder number at -A
^ Installed position: Marking -B- faces pulley end
6. Dowel
^ Dowel must seat securely in connecting rod, not in bearing cap
7. Bearing shell
^ Note version: upper bearing shell (toward piston) in wear resistant material. Identification: black line on running surface close to separation edge.
^ Note installed position
^ Do not interchange used bearing shells
^ Axial clearance:
Wear limit: 0.37 mm
^ Check radial clearance with Plastigage:
Wear limit: 0.08 mm. Do not rotate crankshaft while checking.
8. Cylinder block
^ Checking cylinder bores see Fig. 3
^ Piston and cylinder dimensions
9. Connecting rod bearing cap
^ Mark cylinder number at -A
^ Note installed position
^ Installed position: Marking -B-faces pulley end
10. Oil spray jet
^ For piston cooling
11. 25 Nm (18 ft. lbs.)
^ Install without sealant
12. Connecting rod bolt
^ 30 Nm (22 ft. lbs.) + additional 1/4 turn (90°)
^ Always replace
^ Oil the threads and contact surfaces
^ Use old bolts to measure radial clearance
^ Torque angle can be measured with Hazet 6690 torque angle meter or equivalent.





Fig. 1 Piston ring gap, checking

Special tools
^ Feeler gauge





- Squarely insert ring into top of cylinder and push it down to approx. 15 mm from lower edge of cylinder.





Fig. 2 Ring to groove clearance, checking

Special tools
^ Feeler gauge





- Clean groove before checking.

Fig. 3 Cylinder bores, checking

Special tools
^ Internal dial gauge 50 to 100 mm

- Take measurements at 3 positions in both lateral -A- and longitudinal -B- directions, as illustrated.
^ Deviation from nominal dimension: 0.10 mm maximum

Note: Do NOT measure the cylinder bores when the block is mounted on a repair stand using the VW 540 adaptor bracket. Bending stresses resulting from the mass overhang will make incorrect measurements likely.





Fig. 4 Piston installation position and piston/cylinder allocation
Piston in cylinders 1 and 2:
Larger intake valve chamber points toward flywheel (arrows)
Piston in cylinders 3 and 4:
Larger intake valve chamber points toward belt pulley side (arrows).

Note: New piston/cylinder allocations are shown by a colored mark on the piston crown.

^ Piston for cylinder 1 and 2: marked 112
^ Piston for cylinder 3 and 4: marked 3/4

Piston projection at TDC, checking
Special tools





^ VW 382/7 measuring bridge





^ VW 385/17 magnetic plate
^ Dial indicator

Checking





Piston projection at TDC must be measured when installing new pistons or a short block. Depending on piston projection, install the corresponding cylinder head gasket using the following table:

Note: To measure the piston position at TDC, tam crankshaft clockwise.





Cylinder head gasket, identification
^ Part No. = arrow 1
^ Production control code = arrow 2 (disregard)
^ Holes = arrow 3

Note: If the measurements of piston projections are different, use the largest measurement to select the proper gasket.





Piston and cylinder dimensions part 1 of 2





Piston and cylinder dimensions part 2 of 2