Audi Workshop Service and Repair Manuals

Pistons and conrods - exploded view

1 -

Bolt

q

Renew

q	Lubricate threads and contact surface

q	30 Nm + turn 90° further

2 -	Conrod bearing cap

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 in colour -B-

q	Installation position: Markings -A- face towards pulley end

3 -	Bearing shell

q	Installation position → Fig.

q	Renew used bearing shells

q	Note version: Upper bearing shell (closest to piston) is constructed from a more wear-resistant material. Distinguishing feature on new bearing shells: black marking on bearing surface near joint

q	Check that it is securely seated

4 -

Conrod

q	Only renew as a complete set

q	With industrially cracked conrod bearing cap

q	Separating parts of new conrod → Fig.

q	Mark cylinder allocation in colour -B-

q	Installation position: Markings -A- face towards pulley end

q	Axial clearance: wear limit: 0.37 mm

q	Measuring radial clearance → Chapter

5 -

Circlip

q

Renew

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	Version fitted in vehicle may differ from illustration

q	Mark installation position and cylinder number → Fig.

q	Checking → Fig.

q	Install using piston ring clamp

q	Piston and cylinder dimensions → Chapter

q	Measuring cylinder bore → Fig.

q	Measuring piston projection at „TDC“ → Chapter

8 -	Piston rings

q	Compression rings

q	Offset gaps by 120°

q	Use piston ring pliers to remove and install

q	Installation position: marking „TOP“ or side with lettering faces towards piston crown

q	Measuring ring gap → Fig.

q	Measuring ring-to-groove clearance → Fig.

9 -	Piston ring

q	Oil scraper ring

q	Offset gap 120° from bottom compression ring

q	Use piston ring pliers to remove and install

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. –  To do so, use a piston without rings.

Piston ring	new mm	Wear limit mm
1st compression ring	0.25 … 0.40	1.00
2nd compression ring	0.25 … 0.40	1.00
Oil scraper ring	0.25 … 0.50	1.00

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

Piston ring	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 –  Using a micrometer (75 ... 100 mm), measure approx. 15 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“.   Note Renew piston if cracking is visible on piston skirt.

Installation position of pistons and allocation of piston/cylinder l  Arrow on piston crown points to pulley end -arrows-.

Measuring cylinder bore –  Use a cylinder gauge -VAS 6078- to take measurements at 3 points in transverse direction -A- and in longitudinal direction -B-. l  Maximum deviation from nominal dimension: 0.10 mm. Nominal dimension → Chapter „Piston and cylinder dimensions“.

Installation position of bearing shells in conrods 1 -  Bearing shell with oil drilling -arrow- for conrod. 2 -  Bearing shell without oil drilling for conrod bearing cap. –  Insert bearing shells centrally in conrod/conrod bearing cap. l  Distance -a- is the same on both sides.

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) l  Installation position: align locating edge of oil spray jet with machined surface of cylinder block.   Caution Avoid damage to oil spray jets. t  Do not bend oil spray jets. t  Always renew bent oil spray jets.