Volkswagen Workshop Service and Repair Manuals

Dismantling and assembling pistons and conrods

1 -	Piston rings

q	Offset gaps by 120°.

q	Remove and install using piston ring pliers.

q	“TOP” faces towards piston crown.

q	Checking ring gap → Fig..

q	Checking ring-to-groove clearance → Fig..

2 -

Piston

q	With combustion chamber.

q	Mark installation position and cylinder number.

q	Installation position and allocation of piston to cylinder → Fig.

q	Arrow on piston crown points to pulley end.

q	Install using piston ring clamp.

q	If piston skirt is cracked, renew piston.

q	Checking piston projection at TDC → Chapter.

3 -	Piston pin

q	If difficult to remove, heat piston to 60 °C.

q	Remove and install with drift -VW 222 A-.

4 -

Circlip

5 -

Conrod

q	Renew as set only.

q	Mark cylinder number -A-

q	Installation position: marking -B- faces towards pulley end

6 -	Fitted pin

q	The dowel pins must sit firmly in the conrod, not in the cover

7 -	Bearing shell

q	Observe different types: on engine code AHF, ASV, upper bearing shell (towards piston) is made of a more wear resistant material and can be identified by a black line on the bearing surface in the area of the joint.

q	Note installation position.

q	Do not interchange used bearing shells.

q	Ensure retaining lug fits tightly in recess

q	Axial clearance wear limit: 0.37 mm.

q	Measure radial clearance with Plastigage: Wear limit: 0.08 mm, do not rotate crankshaft when measuring radial clearance.

8 -	Cylinder block

q	Checking cylinder bores → Fig..

q	Piston and cylinder dimensions → Chapter.

9 -	Conrod bearing cap

q	Note installation position.

10 -	Oil spray jet

q	For piston cooling.

11 -

25 Nm

q	Insert without sealant.

12 -	Conrod bolt, 30 Nm + 1/4 turn (90°) further

q

Renew.

q	Oil threads and contact surface.

q	Use old bolts to measure radial clearance.

Checking piston ring gap –  Push ring squarely from above down to approx. 15 mm from bottom end of cylinder.

Piston ring dimensions in mm	New	Wear limit
1st compression ring	0.20 …0.40	1.0
2nd compression ring	0.20 …0.40	1.0
Oil scraper ring	0.25 …0.50	1.0

Checking ring-to-groove clearance Clean groove before check.

Piston ring dimensions in mm	New	Wear limit
1st compression ring	0.06 …0.09	0.25
2nd compression ring	0.05 …0.08	0.25
Oil scraper ring	0.03 …0.06	0.15

Checking cylinder bores Special tools and workshop equipment required t  Internal dial test indicator 50…100 mm –  Measure at 3 positions both across -A- and in-line with engine -B-. Deviation from nominal dimension max. 0.10 mm   Note Cylinder bores must not be measured when cylinder block is mounted on repair stand with engine and gearbox support -VW 540-, as measurements may then be incorrect.

Piston installation position and allocation of piston to cylinder Piston in cylinders 1 and 2: Larger inlet valve recess -arrows- towards flywheel. Piston in cylinders 3 and 4: Larger inlet valve recess -arrows- towards belt pulley end.   Note t  New piston allocation to cylinders is shown by a coloured mark stamped on the piston crown. t  Piston for cylinders 1 and 2: marked 1/2 t  Piston for cylinders 3 and 4: marked 3/4