Audi Workshop Service and Repair Manuals

Pistons and conrods - exploded view

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

q

Renew

q	Lubricate threads and contact surface

q	Use old bolts when measuring radial clearance

q	To measure radial clearance, tighten to 30 Nm but do not turn further

2 -	Conrod bearing cap

q	Mark cylinder number -B-

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

3 -	Bearing shells

q	Upper bearing shell with oil hole for piston pin lubrication

q	Installation position → Fig.

q	Do not interchange used bearing shells (mark positions)

q	Axial clearance (new): 0.10 ... 0.35 mm

q	Axial clearance: wear limit: 0.40 mm

q	Check radial clearance with Plastigage; do not rotate crankshaft when checking radial clearance

q	Radial clearance (new): 0.01 ... 0.05 mm

q	Radial clearance: wear limit: 0.12 mm

4 -

Conrod

q	Only renew as a complete set

q	Mark cylinder number -B-

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

q	With oil drilling for piston pin lubrication

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	Checking → Fig.

q	Mark installation position and cylinder number

q	Arrow on piston crown points to pulley end

q	Install using piston ring clamp

q	Piston and cylinder dimensions → Chapter

q	Checking cylinder bore → Fig.

8 -	Piston rings

q	Offset gaps by 120°

q	Use piston ring pliers to remove and install

q	“TOP” must face towards piston crown

q	Checking ring gap → Fig.

q	Checking ring-to-groove clearance → Fig.

Checking piston ring gap –  Insert ring at right angles 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 (in mm)	New	Wear limit
1st compression ring	0.20 … 0.40	0.8
2nd compression ring	0.20 … 0.40	0.8
Oil scraper ring	0.25 … 0.50	0.8

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	0.20
2nd compression ring	0.05 … 0.08	0.20
Oil scraper ring	0.03 … 0.06	0.15

Checking piston –  Measure pistons approx 10 mm from the lower edge of skirt, at 90° to the piston pin axis. l  Maximum deviation from nominal dimension: 0.04 mm. Nominal dimension → Chapter „Piston and cylinder dimensions“.

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: 0.08 mm. Nominal dimension → Chapter „Piston and cylinder dimensions“.

Installation position of bearing shell –  Insert bearing shells centrally in conrod/conrod bearing cap. l  Dimension -a- = 3.0 mm

Oil spray jet and pressure relief valve 1 -  Oil spray jet for piston cooling 2 -  Bolt with pressure relief valve, 27 Nm l  Opening pressure: 1.3 ... 1.6 bar.