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	Do not interchange

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

q	Note when fitting bearing cap: the wide contact shoulder -A- must point towards same side on conrod and conrod bearing cap

q	Installation position of conrod pairs → Fig.

3 -	Bearing shells

q	Ensure that retaining lugs are securely seated.

q	Do not interchange used bearing shells (mark accordingly, but not on the running surface)

q	Measuring radial clearance → Chapter

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

q	There are oversized bearings available for machined crankshaft conrod journals → Parts catalogue

4 -

Conrod

q	Only renew as a complete set

q	Mark cylinder allocation in colour -B- → Fig.

q	Note when fitting bearing cap: the wide contact shoulder -A- must point towards same side on conrod and conrod bearing cap

q	Installation position of conrod pairs → Fig.

q	Axial clearance for each conrod pair (when new): 0.20 … 0.38 mm

q	Wear limit (axial clearance): 0.60 mm

q	Measuring radial clearance → Chapter

5 -	Piston pin

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

q	Remove and install using drift -VW 222 A-

6 -

Circlip

7 -

Piston

q	Installation position for piston → Fig.

q	Piston and cylinder dimensions → Chapter

q	Checking → Fig.

q	Install using piston ring clamp

q	Measuring cylinder bore → Fig.

8 -	Piston rings

q	Offset gaps by 120°

q	Use piston ring pliers to remove and install

q	Marking “TOP” or side with identification mark must face piston crown

q	Measuring ring gap → Fig.

q	Measuring ring-to-groove clearance → Fig.

Measuring 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	0.25 … 0.40	0.8
2nd compression ring	0.20 … 0.40	0.8
Oil scraper ring	–	0.4

Measuring ring-to-groove clearance –  Clean groove in piston before checking clearance.

Piston ring (in mm)	New	Wear limit
1st compression ring	0.04 … 0.08	0.20
2nd compression ring	0.005 … 0.045	0.20
Oil scraper ring	0.01 … 0.05	0.15

Checking piston –  Using a micrometer (75 ... 100 mm), measure approx. 10 mm from the lower edge, perpendicular to the piston pin axis. l  Max. deviation from nominal dimension: 0.04 mm. Nominal dimension → Chapter.

Measuring cylinder bore –  Use 50 ... 100 mm internal dial gauge to take measurements at 3 points in transverse direction -A- and longitudinal direction -B-. l  Max. deviation from nominal dimension: 0.08 mm. Nominal dimension → Chapter.

Installation position of pistons –  Use chalk or waterproof felt-tip pen to mark cylinder allocation on piston crown.   Note Do not use a centre punch or scriber, as this would damage the coating of the piston crown. Installation position: l  Arrows on piston crowns point to pulley end. l  Valve recesses -1- point to centre of engine.

Marking conrods   Note t  Only renew conrods as a complete set. t  Do not interchange conrod bearings. –  Prior to removal, use a coloured pen to mark conrod and conrod bearing cap relative to one another, as well as to cylinder -arrow-.

Conrod installation position l  The cast lugs -arrows- on the ground surfaces of conrod pairs 1 and 2, 3 and 4, 5 and 6, and 7 and 8 must face one another.

Oil spray jet for piston cooling 1 -  Oil spray jet (opening pressure: 2 ... 2.4 bar) 2 -  Bolts, 9 Nm. Install using locking fluid; for locking fluid refer to → Parts catalogue