Audi Workshop Service and Repair Manuals

Pistons and conrods - exploded view

1 -	Conrod bolt

q	On vehicles with 1.8 ltr. engine: 30 Nm + turn 90° further

q	On vehicles with 2.0 ltr. engine: 45 Nm + 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 -	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 allocation -A-

q	Installation position: Marking -B- faces towards pulley end

3 -	Bearing shells

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

4 -	Pressure relief valve

27 Nm

5 -	Oil spray jet

q	For piston cooling

6 -

Circlip

7 -	Piston pin

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

q	Remove and install using drift -VW 222 A-

8 -

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.

9 -	Compression rings

q	Offset gaps by 120°

q	Use piston ring pliers to remove and install

q	“TOP” or “R” must face towards piston crown

q	Checking ring gap → Fig.

q	Checking ring-to-groove clearance → Fig.

10 -	Oil scraper ring

q

2 parts

q	Offset gap of top steel element of piston ring by 120° to next compression ring.

q	“TOP” or “R” must face towards piston crown

q	Offset gaps of individual parts of oil scraper ring.

q	Checking ring gap → Fig.

q	Ring-to-groove clearance cannot be checked.

11 -

Conrod

q	Only renew as a complete set

q	Mark cylinder allocation -A-

q	Installation position: Marking -B- faces towards pulley end

q	Separating parts of new conrod → Chapter

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	0.80
Oil scraper ring	0.25...0.50	0.80

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

Piston ring Dimensions in mm	New	Wear limit
1st compression ring	0.06 … 0.09	0.20
2nd compression ring	0.03 … 0.06	0.15
Oil scraper rings	Cannot be measured

Checking piston –  Measure pistons approx 10 mm from the lower edge of skirt, at 90° to the piston pin axis. t  Difference between actual and nominal diameter: not more than 0.04 mm.

Checking cylinder bore Special tools and workshop equipment required t  Cylinder gauge, 50 ... 100 mm.   Caution Machining (reboring, honing, grinding) cylinder bore with workshop equipment is not permitted. The surface of the cylinder bore is damaged by machining. –  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.   Note Measuring the cylinder bores must not be done when the cylinder block is mounted to the engine and gearbox stand -VAS 6095-, as incorrect measurements may result.

Installation position of bearing shell –  Position bearing shells in centre of conrod and conrod bearing cap when fitting. Dimension -a- must be identical on both sides.