Audi Workshop Service and Repair Manuals

Pistons and conrods - exploded view of components

1 -	Piston rings

q	Offset gaps by 120°

q	Remove and install using piston ring clamp

q	Marking “TOP” or inscription must face 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 allocation

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

q	Arrow on piston crown points to pulley end

q	If cracking is visible on piston skirt, renew piston

q	Checking cylinder bore → Fig.

q	Piston and cylinder dimensions → Chapter

q	Install using piston ring clamp

q	Checking piston projection at TDC → Chapter

3 -	Piston pin

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

q	Remove and install using drift -VW 222 A-

4 -

Circlip

5 -

Conrod

q	Only renew as a complete set

q	Mark cylinder allocation -A-

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

6 -	Bearing shell

q	Installation position → Fig.

q	Do not interchange used bearing shells (mark positions)

q	Note type: upper bearing shell (closest to piston) is constructed from more wear-resistant material. Distinguishing feature on new bearing shells: black marking on contact surface near separating point

q	Check that it is securely seated

q	Axial clearance: wear limit: 0.37 mm

q	Check radial clearance with Plastigage

q	Do not rotate crankshaft when checking radial clearance

q	Radial clearance: wear limit: 0.08 mm

7 -	Cylinder block

q	Checking cylinder bore → Fig.

q	Piston and cylinder dimensions → Chapter

8 -	Conrod bearing cap

q	Note installation position

9 -	Oil spray jet

q	For piston cooling

q	Note installation position: Turn oil spray jet anti-clockwise until it makes contact with cylinder block and secure in this position

10 -

27 Nm

q	Insert without sealant

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

q

Renew

q	Lubricate threads and contact surface

q	Use old bolt for measuring radial clearance

Checking piston ring gap –  Insert ring at right angle to cylinder wall from above and push down into lower cylinder opening approx. 15 mm from bottom of cylinder. To do so, use a piston without rings.

Piston ring Dimensions in mm	New	Wear limit 1)
1st compression ring	0.20 … 0.35	–
2nd compression ring	0.90 … 1.15	–
Oil scraper ring	0.25 … 0.50	–
l  1) No wear limit specified.

Checking ring-to-groove clearance –  Clean groove in piston before checking clearance.

Piston ring Dimensions in mm	New	Wear limit
1stcompression 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

Piston installation position and piston/cylinder allocation Pistons in cylinders 1 and 2: l  Larger inlet valve chamber towards flywheel -arrows-. Piston in cylinder 3: l  Larger inlet valve chamber towards belt pulley side -arrow-.   Note t  With new pistons, cylinder allocation is indicated by a coloured marking on piston crown. t  Piston for cylinder 1 and 2: marked 1/2. t  Piston for cylinder 3: marked 3.

Checking cylinder bore –  Use 50 ... 100 mm internal dial gauge to take measurements at 3 points in transverse direction -A- and longitudinal direction -B-. l  Difference between measured value and nominal value: max. 0.10 mm. Nominal dimension → Chapter „Piston and cylinder dimensions“.   Note Measuring the cylinder bores must not be done when the cylinder block is mounted on a repair stand with engine and gearbox support -VW 540-, as incorrect measurements may result.

Installation position of bearing shell –  Insert bearing shells in centre of conrod/conrod bearing cap. l  Dimension -a- = 2.5 mm.