Audi Workshop Service and Repair Manuals

Pistons and conrods - exploded view

1 -	Piston rings

q	Offset gaps by 120°

q	Use piston ring pliers to remove and install

q	Marking „TOP“ or inscription must face piston crown.

q	Checking ring gap → Fig.

q	Checking ring-to-groove clearance → Fig.

2 -

Piston

q	With combustion chamber

q	Mark installation position and cylinder number

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

q	Arrow on piston crown points to pulley end

q	If cracking is visible on piston skirt, renew piston

q	Checking piston → Fig.

q	Piston and cylinder dimensions → Chapter

q	Checking cylinder bore → Fig.

q	Install using piston ring clamp

q	Measuring piston projection at TDC → Chapter

3 -	Piston pin

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

q	Remove and install using drift -VW 222 A-

4 -

Circlip

q

Renew

5 -

Conrod

q	Mark cylinder allocation -A-

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

q	With industrially cracked conrod bearing cap

q	Separating parts of new conrod → Fig.

q	Axial clearance: wear limit: 0.37 mm

q	Measuring radial clearance → Chapter

6 -	Bearing shell

q	Installation position → Fig.

q	Mark used bearing shells for re-installation but not on bearing surface

q	Bearing shells worn down to the base layer must be renewed

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 bearing surface near joint

q	Check that it is securely seated

7 -	Cylinder block

q	Checking cylinder bore → Fig.

q	Piston and cylinder dimensions → Chapter

8 -	Conrod bearing cap

q	Note installation position

q	Since industrially cracked conrods are used (the conrod is cast as one unit and the cap is then cracked off), the conrod bearing cap can only be fitted in one position on the corresponding conrod

9 -	Oil spray jet

q	For piston cooling → Fig.

10 -

27 Nm

q	Insert without sealant

11 -	Conrod bolt, 30 Nm + 90° further

q

Renew

q	Lubricate threads and contact surface

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. To do so, use a piston without rings.

1.9 ltr. engine	new mm	Wear limit mm
1st compression ring	0.30 … 0.40	1.00
2nd compression ring	0.20 … 0.45	1.00
Oil scraper ring	0.25 … 0.55	1.00

2.0 ltr. engine	new mm	Wear limit mm
1st compression ring	0.30 … 0.40	1.00
2nd compression ring	0.30 … 0.50	1.00
Oil scraper ring	0.25 … 0.50	1.00

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

1.9 ltr./2.0 ltr. engine	new mm	Wear limit mm
1st compression ring	0.06 … 0.09	0.25
2nd compression ring	0.05 … 0.08	0.25
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. l  Maximum deviation from nominal dimension: 0.04 mm. Nominal dimension → Chapter „Piston and cylinder dimensions“.

Piston installation position and piston/cylinder allocation Pistons in cylinders 1 and 2: l  Large cut-out for inlet valve faces flywheel end -arrows-. Pistons in cylinders 3 and 4: l  Large cut-out for inlet valve faces pulley end -arrows-.   Note t  With new pistons, cylinder allocation is indicated by a coloured marking on piston crown. t  Piston for cylinder 1 and 2: marked 1/2. t  Piston for cylinder 3 and 4: marked 3/4.

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: 0.10 mm. Nominal dimension → Chapter „Piston and cylinder dimensions“.

Installation position of bearing shell –  Insert bearing shells centrally in conrod/conrod bearing cap. l  Distance -a- = 2.5 mm.

Separating parts of new conrod It is possible that the two parts of a new conrod are not completely separated as intended. If it is not possible to take off the conrod bearing cap by hand, proceed as follows: –  To avoid any risk of damage, the conrod should only be clamped lightly in a vice using jaw covers as shown in illustration. l  The conrod is clamped in position below the dotted line. –  Unscrew bolts -arrows- approx. 5 turns.

–  Using a plastic hammer, carefully knock conrod bearing cap loose -arrow-.

Oil spray jet and pressure relief valve 1 -  Bolt with pressure relief valve, 27 Nm 2 -  Oil spray jet (for cooling of pistons)   Note t  Take care not to bend oil spray jets. t  Always renew bent oil spray jets.