Piston: Service and Repair

Pistons and connecting rods, disassembling and assembling
Vehicles with engine code: AWD





1-Piston ring
^ Offset gaps by 120
^ Remove and install with piston ring pliers
^ "TOP" faces towards piston crown
^ Checking ring gap see Fig. 1
^ Checking ring to groove clearance see F-2
^ 2 or 3 part oil scraper ring, mixed installations permissible
2-Piston
^ Checking see Fig
^ Mark installation position and cylinder number
^ Arrow on piston crown points to pulley end
^ Install using piston ring clamp
3-Connecting rod
^ Only replace as a set
^ Mark cylinder number-B
^ Installation position: Marking-A-faces towards pulley end
4-Connecting rod bearing cap
^ Installation position: Marking-A-faces towards pulley end
^ Mark cylinder number-B
5-30 Nm + 1/4 turn (90°) further
- Always replace
- Oil threads and contact surface
- To measure radial clearance tighten to 30 Nm but not further
6-Pressure relief valve, 27 Nm
^ Opening pressure: 1.3 to 1.6 bar
7-Oil spray jet
^ For piston cooling
8-Bearing shell
^ Note installation position
^ Do not interchange used bearing shells
^ Make sure retaining lugs fit tightly in recesses
- Axial clearance New: 0.10 to 0.31 mm Wear limit: 0.40 mm
- Check radial clearance with Plastigage: New: 0.01 to 0.05 mm Wear limit: 0.09 mm Do not rotate crankshaft when checking radial clearance
9-Cylinder block
^ Checking cylinder bores-Fig. 4
^ Piston and cylinder dimensions
10-Connecting rod bolt
^ Always replace
11-Circlip
12-Piston pin
^ If difficult to remove, heat piston to 60°C
^ Remove and install with VW 222a





Fig. 1 Checking piston ring gap
^ Special tools and equipment
^ Feeler gauges





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





Fig. 2 Checking ring to groove clearance
Special tools and equipment
^ Feeler gauges





- Clean groove before check.





Fig. 3 Checking piston
Special tools and equipment
^ Micrometer 75 to 100 mm
Measure pistons approx. 10 mm from the lower edge of skirt, at 90° to the piston pin axis.
Deviation from nominal dimension max. 0.04





Fig. 4 Checking cylinder bores
Special tools and equipment
^ Internal dial gauge 50 to 100 mm
^ Measure bores at 3 locations in both directions-A-across the engine and-B-in line with crankshaft.
^ Deviation from nominal dimension max. 0.10 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





Piston and cylinder dimensions (engine code AWD)