Audi Workshop Service and Repair Manuals

Piston with sawn conrod - exploded view

Oil spray jet and pressure relief valve → Fig.

1 -	Piston 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	Measuring ring gap → Fig.

q	Measuring ring-to-groove clearance → Fig.

2 -

Piston

q	Mark installation position and cylinder number

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

q	If cracking is visible on piston skirt, renew piston

q	Arrow on piston crown points to pulley end

q	Install using piston ring clamp

q	Measuring piston projection at TDC → Chapter

q	Piston and cylinder dimensions → Chapter

q	Checking → Fig.

3 -	Piston pin

q	If difficult to move, heat piston to approx. 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 number -B-

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

q	Measuring radial clearance → Chapter

6 -	Bearing shell

q	Installation position → Fig.

q	Renew used bearing shells

q	Note version: Upper bearing shell (towards piston) made of a more wear-resistant material; new bearing shells can be identified by a black line on bearing surface in area of joint

q	Insert bearing shells centrally

q	Check that it is securely seated

q	Axial clearance: wear limit: 0.37 mm

q	Measuring radial clearance → Chapter

7 -	Cylinder block

q	Measuring cylinder bore → Fig.

q	Piston and cylinder dimensions → Chapter

8 -	Conrod bearing cap

q	Mark cylinder number -B-

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

9 -	Conrod bolt, 30 Nm + turn 90° further

q

Renew

q	Lubricate threads and contact surface

Measuring 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	new mm	Wear limit mm
1st compression ring	0.25 … 0.40	1.0
2nd compression ring	0.25 … 0.40	1.0
Oil scraper ring	0.25 … 0.50	1.0

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

Piston ring	new mm	Wear limit mm
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 –  Using a micrometer (75 ... 100 mm), measure approx. 10 mm from the lower edge, perpendicular to the piston pin axis. l  Maximum deviation from nominal dimension: 0.04 mm.

Piston installation position and piston/cylinder allocation –  Mark installation position and assignment on inside of pistons (not on piston crown) with an electric marker or felt-tip pen. Pistons in cylinders 1 and 2: l  Larger inlet valve chamber towards flywheel -arrows-. Pistons in cylinders 3 and 4: l  Larger inlet valve chamber towards pulley end -arrows-.   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 and 4: marked “3/4”. t  In addition, the arrow stamped into piston crown points to pulley end.

Measuring 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 shell –  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 piston cooling