Audi Workshop Service and Repair Manuals

Pistons and conrods - exploded view of components   Note t  Oil spray jet and pressure relief valve → Fig. t  If large quantities of metal shavings or particles are found in the engine oil when repairing the engine, the oil passages must be cleaned carefully, and the oil cooler must be renewed in order to prevent further damage occurring later.

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

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; wear limit: 0.40 mm

q	Check radial clearance with Plastigage: New: 0.01 ... 0.05 mm; Wear limit: 0.12 mm. Do not rotate crankshaft when checking radial clearance

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 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	0.20 … 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 approx. 10 mm from the bottom edge, perpendicular to the piston pin axis. l  Difference between measured value and nominal value: max. 0.04 mm

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. 0.08 mm

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