Audi Workshop Service and Repair Manuals

Pistons and conrods - exploded view

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

q

Renew

q	Lubricate threads and contact surface

q	Use old bolts when measuring radial clearance

2 -	Conrod bearing cap

q	Mark cylinder number -B-

q	Installation position: Markings -A- face towards pulley end

3 -	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 made of more wear-resistant material. Distinguishing feature on new bearing shells: black marking on bearing surface near joint

q	Check that it is securely seated

q	Axial clearance: wear limit: 0.37 mm

q	Measuring radial clearance → Chapter

4 -

Conrod

q	Only renew as a complete set

q	Mark cylinder number -B-

q	Installation position: Markings -A- face towards pulley end

5 -

Circlip

6 -	Piston pin

q	If difficult to move, heat piston to approx. 60 °C

q	Remove and install using drift -VW 222 A-

7 -

Piston

q	With combustion chamber

q	Mark installation position and cylinder number

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 piston → Fig.

q	Piston and cylinder dimensions → Chapter

q	Checking cylinder bore → Fig.

q	Install using piston ring clamp

q	Checking piston projection at TDC → Chapter

8 -	Piston rings

q	Compression rings

q	Offset gaps by 120°

q	Use piston ring pliers to remove and install

q	Marking “TOP” or inscription must face piston crown.

q	Checking ring gap → Fig.

q	Checking ring-to-groove clearance → Fig.

9 -	Piston ring

q	Oil scraper ring

q	Offset gap 120° from bottom compression ring

q	Use piston ring pliers to remove and install

q	Checking ring gap → Fig.

q	Checking ring-to-groove clearance → Fig.

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. Use a piston without rings to push ring into bore.

Piston ring (in mm)	New	Wear limit
1st compression ring	0.25 … 0.40	1.00
2nd compression ring	0.25 … 0.40	1.00
Oil scraper ring	0.25 … 0.50	1.00

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

Piston ring (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 piston –  Measure approx. 10 mm from the bottom edge, perpendicular to the piston pin axis. l  Maximum deviation from nominal dimension: 0.04 mm.

Piston installation position and piston/cylinder allocation l  Arrow on piston crown points to pulley end -arrows-.

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  Maximum deviation from nominal dimension: 0.10 mm.

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

Oil spray jet and pressure relief valve 1 -  Bolt with pressure relief valve, 27 Nm 2 -  Oil spray jet (for cooling of pistons)