Connecting Rod: Service and Repair

Piston and connecting rod, disassembling and assembling





1. Piston rings
^ Offset gaps by 120°
^ Use piston ring pliers to remove and install
^ "TOP" faces towards piston crown
^ Checking ring gap
^ Checking ring to groove clearance
2. Piston
^ Checking, Refer to Fig. 3
^ Mark installation position to connecting rod and cylinder
^ Flatter side of piston crown faces toward center of cylinder block
^ Install with piston installation tool (funnel) 3278, Refer to Fig. 5
3. Snap ring
4. Conrad
^ Only replace as a set
^ Mark position to cylinder -B
^ Installation position: Marks -A- must be aligned above one another
5. Bearing shell
^ Observe installation position
^ Do not interchange used bearing shells
^ Lugs on bearing shells must fit tightly in recesses
^ Axial clearance, New: 0.05 0.35 mm, Wear limit: 0.40 mm
^ Check radial clearance with Plastigage: New: 0.02 0.07 mm, Wear limit: 0.10 mm. Do not turn crankshaft when checking radial clearance
6. Conrad bearing cap
^ Mark position to cylinder -B
^ Installation position: Marks -A- must be aligned above one another
7. 30 Nm plus additional 1/4 turn (90°) further
^ Replace
^ Oil thread and contact surface
^ To measure radial clearance tighten to 30 Nm, but do not turn further
8. Cylinder block
^ Checking cylinder bore
^ Removing and installing crankshaft, Refer to Crankshaft,Engine, Service and Repair
^ Piston and cylinder dimensions, Refer to Piston,Engine, Specifications, Mechanical
9. Piston pin
^ If difficult to remove, heat piston to 60°C
^ Remove and install with drift VW 222a





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





Test sequence
- Push ring squarely from above down to approximately 15 mm from bottom end of cylinder. To do this use a piston without rings.





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





Test sequence
- Clean ring groove before checking.





Fig. 3 Checking piston
Special tools and equipment
^ External micrometer 75. . . 100 mm

Test sequence
- Take measurement approximately 6 mm from lower edge of piston skirt and offset 90° to piston axis.
Deviation from nominal dimension: max. 0.04 mm





Fig. 4 Checking cylinder bores
Special tools and equipment
^ Internal dial gauge 50 100 mm

Test sequence
- Measure bores at 3 locations in both directions -A- across engine and -B- in line with crankshaft.
Deviation from nominal dimension: max. 0.08 mm

Note: The cylinder bores must not be measured if the cylinder block is mounted on a repair stand with engine bracket 3269 or VW 540, as incorrect measurements would then result.





Fig. 5 Installing pistons with piston installation tool (funnel) 3278
Special tools and equipment
^ 3278 Funnel

Note: If a new installation tool (funnel) is used to install the pistons, first pass piston with oiled piston rings through the funnel twice and remove the resulting metal shavings if necessary. Only then install piston with piston rings.

Work sequence
- Push piston by hand into oiled installation tool (funnel). Flat side of piston crown must face toward tab on funnel -arrow-.
- Hold installation tool (funnel) on upper edge and press piston in with both thumbs.
- Push piston in until it protrudes approximately 15 mm from lower edge of tool (funnel).
- Insert piston into appropriate cylinder bore. Tab on tool (funnel) -arrow- must face center of cylinder block.
- Press installation tool (funnel) tightly against cylinder block and push piston in.