Audi Workshop Service and Repair Manuals

Pistons and conrods - exploded view of components

Oil spray jet for piston cooling → Fig..

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

q

Renew

q	Lubricate threads and contact surface

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

2 -	Conrod bearing cap

q	Note installation position: split contact surfaces on side of conrod must be in alignment -B-

3 -	Bearing shell

q	Note installation position

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 contact surface near separating point

q	Check that it is securely seated

q	Measuring radial clearance → Chapter

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

4 -

Conrod

q	Only renew as a complete set

q	Mark cylinder allocation -A- → Fig.

q	Note when fitting bearing cap: split contact surfaces on side of conrod must be in alignment -B-

q	Installation position of conrod pairs → Fig.

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	Mark installation position and cylinder number → Fig.

q	Arrow on piston crown points to pulley end

q	Checking → Fig.

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 Dimensions in mm	New	Wear limit
1st compression ring	0.35 … 0.50	1.0
2nd compression ring	0.50 … 0.70	1.4
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 rings	0.02 … 0.08	0.10
Oil scraper ring	0.02 … 0.08	0.10

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. 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“

Piston installation position and piston/cylinder allocation –  Use chalk or waterproof felt-tip pen to mark installation position and cylinder allocation on piston crown.   Note Do not use a centre punch or scriber, as this would damage the coating of the piston crown. l  Installation position: Arrow on piston crown points to pulley end.

Marking conrods   Note t  Only renew conrods as a complete set. t  Do not interchange conrod bearings. –  Before removing, mark mating positions of conrods and conrod bearing caps with coloured pen -arrow-.

Installation position of conrod pairs l  The cast lugs -arrows- at ground surfaces of conrod pairs 1 and 2, 3 and 4, and 5 and 6 must face one another.

Oil spray jet for piston cooling 1 -  Bolt, 10 Nm 2 -  Oil spray jet for piston cooling