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

q	When measuring radial clearance, tighten used bolt to 30 Nm but not further

2 -	Conrod bearing cap

q	Mark cylinder allocation before removing -A-

q	Installation position: marking -B- faces towards pulley end (apply marking before removal if no marking is visible)

3 -	Bearing shells

q	Upper bearing shell with oil hole for piston pin lubrication

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

q	Measuring preload → Fig.

4 -

Conrod

q	Only renew as a complete set

q	Mark cylinder allocation before removing -A-

q	Installation position: marking -B- faces towards pulley end (apply marking before removal if no marking is visible)

q	Guided axially via piston

q	Measuring radial clearance → Chapter

5 -	Piston pin

q	If difficult to remove, heat piston to 60 °C

q	Remove and install using drift -VW 222 A-

6 -

Circlip

q

Renew

7 -

Piston

q	Checking → Fig.

q	Mark installation position and cylinder number

q	Installation position: arrow on piston crown points to pulley end

q	Install using piston ring clamp

q	Checking cylinder bore → Fig.

q	Piston and cylinder dimensions → Chapter

8 -	Compression ring

q	Use piston ring pliers to remove and install

q	Pay attention to cross section

q	Offset gap by 120° to next compression ring

q	Inscription „TOP“ faces towards piston crown

q	Checking ring gap → Fig.

q	Checking ring-to-groove clearance → Fig.

9 -	Compression ring

q	Use piston ring pliers to remove and install

q	Pay attention to cross section

q	Offset gap 120° relative to adjacent oil scraper ring

q	Inscription „TOP“ faces towards piston crown

q	Checking ring gap → Fig.

q	Checking ring-to-groove clearance → Fig.

10 -	Oil scraper ring

q

3 parts

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

q	Offset gaps of individual parts of oil scraper ring

q	Checking ring gap → Fig.

q	Ring-to-groove clearance cannot be checked

Checking piston ring gap –  Insert piston 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 Dimensions in mm	New	Wear limit
1st compression ring	0.20 … 0.50	1.00
2nd compression ring	0.40 … 0.70	1.00
Oil scraper ring	0.40 … 1.40	No wear limit data available

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

Piston ring Dimensions in mm	New	Wear limit
1st compression ring	0.04 … 0.08	0.15
2nd compression ring	0.04 … 0.08	0.15
Oil scraper ring	Cannot be measured

Checking piston –  Using a micrometer (75 ... 100 mm), measure approx. 12 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“.

Checking cylinder bore –  Use an internal dial gauge -VAS 6078- to take measurements at 3 points in transverse direction -A- and in longitudinal direction -B-. l  Maximum deviation from nominal dimension: 0.08 mm. Nominal dimension → Chapter „Piston and cylinder dimensions“.   Note Do not mount cylinder block on engine and gearbox support -VAS 6095-, as incorrect measurements may result.

Measuring bearing shell preload –  Use caliper gauge to determine dimension -a- for bearing shell and dimension -b- for conrod diameter.    Preload = Distance -a- – distance -b- l  Specification: at least 1.5 mm. –  If the specification is not attained, renew bearing shell.