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	Mark cylinder allocation -A- with coloured pen

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

q	With industrially cracked bearing caps on engine codes AJM, ATD, AUY, ASZ, AXR

q	With conventional bearing caps on engine codes ASZ, ARL

6 -	Bearing shell

q	Note installation position.

q	Note version: Upper bearing shell (towards piston) is made of a more wear resistant material. Identification: Black line on bearing surface in area of joint.

q	Do not interchange used bearing shells.

q	Insert bearing shells centrally.

q	Check for secure seating.

q	Axial clearance wear limit: 0.37 mm.

q	Check radial clearance with Plastigage: Wear limit: 0.08 mm, do not rotate crankshaft when checking radial clearance

7 -	Cylinder block

q	Checking cylinder bores → Fig..

q	Piston and cylinder dimensions → Chapter.

8 -	Conrod bearing cap

q	Note installation position.

q	Vehicles with engine codes AJM, ATD, AUY, ASZ and AXR: bearing caps only fit in one position and only on associated conrod due to nature of separating procedure (industrially cracked).

9 -	Oil spray jet

q	For piston cooling.

10 -

25 Nm

q	Insert without sealant.

11 -	Conrod bolt, 30 Nm + 90° further

q

Renew

q	Oil threads and contact surface.

q	Use old bolts to measure radial clearance.

Checking piston ring gap Special tools and workshop equipment required t  Feeler gauges Test procedure –  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 Special tools and workshop equipment required t  Feeler gauges Test procedure –  Clean ring groove before checking.

Piston ring dimensions in mm	New	Wear limit
1. compression ring	0.06 …0.09	0.25
2. 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 Test procedure –  Measure at 3 positions both across -A- and in-line with engine -B-. Difference between actual and nominal diameter: not more than 0.10 mm.   Note Cylinder bores must not be measured when cylinder block is mounted on a repair stand with engine and gearbox support -VW 540-, as measurements may then be incorrect.

Piston installation position and piston allocation 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