Audi Workshop Service and Repair Manuals

Dismantling and assembling pistons and conrods

1 -	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	Do not interchange

q	Mark cylinder allocation with a coloured pen -B- → Fig.

q	Installation position: Note position of lugs -A- on casting → Fig.

3 -	Bearing shell

q	Note installation position

q	Do not interchange used bearing shells (mark positions)

q	Bearing shells worn down to nickel layer must be renewed

q	Axial clearance of one pair of conrods New: 0.20 ... 0.44 mm; Wear limit: 0.60 mm

q	Measuring radial clearance → Chapter

4 -

Conrod

q	Only renew as a complete set

q	Mark cylinder allocation with a coloured pen -B- → Fig.

q	Installation position: Note position of lugs -A- on casting → Fig.

q	Measuring radial clearance → Chapter

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	With combustion chamber

q	Mark installation position and cylinder number

q	Checking → Fig.

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

q	Arrow on piston crown faces centre of engine

q	Install using piston ring clamp

q	If cracking is visible on piston skirt, renew piston

q	Checking piston projection at “TDC” → Chapter

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.

9 -

9 Nm

10 -	Oil spray jet

q	For piston cooling

Checking piston ring gap –  Insert ring at right angles from above and push down into cylinder approx. 15 mm from bottom end of cylinder.

Piston ring Dimensions in mm	New	Wear limit
1st compression ring	0.20 … 0.40	0.8
2nd compression ring	0.80 … 1.00	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
1st compression ring	0.100 … 0.135	0.150
2nd compression ring	0.045 … 0.085	0.110
Oil scraper ring	0.025 … 0.065	0.090

Checking piston –  Measure approx. 10 mm from the bottom edge, perpendicular to the piston pin axis. l  Difference between actual and nominal diameter: not more than 0.05 mm.

Checking cylinder bore –  Use 50 ... 100 mm internal dial gauge (commercially available) to take measurements at 3 points in transverse direction -A- and longitudinal direction -B-. l  Difference between actual and nominal diameter: not more than 0.08 mm.

Piston installation position and piston/cylinder allocation   Note Pistons in cylinders 1 ... 3 and 4 ... 6 are different. l  Installation position: arrows on piston crown must face centre of engine. –  Mark sequence with waterproof felt-tip pen on piston crown.   Caution Do not use centre punch, as this could lead to subsequent damage (cracks). t  With new pistons, cylinder assignment is shown by a coloured or engraved marking on piston crown. t  Pistons for cylinders 1, 2 and 3 are marked “1/2/3” t  Pistons for cylinders 4, 5 and 6 are marked “4/5/6” t  Piston identification → Chapter.

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-.

Conrod installation position l  Lugs on castings -arrows- → Chapter are located on conrods as shown in illustration.   Note Illustration shows front pair of conrods.