Audi Workshop Service and Repair Manuals

Dismantling and assembling pistons and conrods

1 -	Conrod bolt, 30 Nm + 1/4 turn (90 °) 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 -	Pressure relief valve, 27 Nm

q	Opening pressure: 1.6 ... 1.9 bar

3 -	Oil spray jet

q	For piston cooling

4 -	Conrod bearing cap

q	Note installation position

q	Due to the cracking method used to separate the bearing cap from the conrod in manufacture, the caps only fit in one position and only on the appropriate conrod.

q	Mark cylinder number -B-

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

5 -	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 when new: 0.10...0.35 mm; wear limit: 0.40 mm

q	Check radial clearance with Plastigage - (new): 0.02 ... 0.06 mm; wear limit: 0.09 mm. Do not turn crankshaft when measuring radial clearance

6 -

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

7 -

Circlip

8 -	Piston pin

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

q	Remove and install using drift -VW 222 A-

9 -

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.

10 -	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 Dimensions in mm	New	Wear limit
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 Dimensions in mm	New	Wear limit
Compression ring	0.06...0.09	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. t  Deviation from nominal dimension: max. 0.04 mm

Checking cylinder bore Special tools and workshop equipment required t  Cylinder dial gauge 50...100 mm –  Take measurements at 3 positions in both lateral direction -A- and longitudinal direction -B-. t  Difference between actual and nominal diameter: not more than 0.08 mm.

Installation position of bearing shell Bearing shell -1- with oil drilling -arrow- for conrod. Bearing shell -2- without oil drilling for conrod bearing cap. –  Position bearing shells in centre of conrod and conrod bearing cap when fitting. Dimension -a- must be identical on both sides.