Audi Workshop Service and Repair Manuals

Pistons and conrods - exploded view

1 -

Bolts

q

Renew

q	Lubricate threads and contact surface

q	35 Nm + turn 90° further

2 -	Conrod bearing cap

q	Mark installation position for re-installation

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

q	Installation position: Note position of lugs on casting -A-

3 -	Bearing shells

q	Note installation position

q	Renew used bearing shells

q	Measuring radial clearance → Chapter

4 -

Conrod

q	Only renew as a complete set

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

q	Installation position: Note position of lugs on casting -A- and → Fig.

q	Axial clearance for each conrod pair (when new): 0.20 … 0.44 mm

q	Measuring radial clearance → Chapter

5 -

Circlip

q

Renew

6 -	Piston pin

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

q	Remove and install using drift -VW 222 A-

7 -

Piston

q	Mark installation position and cylinder number → Fig.

q	Renew piston if cracking is visible on piston crown or piston skirt

q	Checking → Fig.

q	Measuring cylinder bore → Fig.

q	Piston and cylinder dimensions → Chapter

q	Install using piston ring clamp

q	Measuring piston projection at „TDC“ → Chapter

8 -	Piston rings

q	Offset gaps by 120°

q	Use piston ring pliers to remove and install

q	Inscription „TOP“ faces towards piston crown

q	Measuring ring gap → Fig.

q	Measuring ring-to-groove clearance → Fig.

Oil spray jet for piston cooling 1 -  Bolt, 9 Nm 2 -  Oil spray jet with spray nozzle valve for piston cooling   Note t  Take care not to bend oil spray jets. t  Always renew bent oil spray jets.

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 … 0.38	0.80
2nd compression ring	0.70 … 0.90	1.30
Oil scraper ring	Max. 0.40	0.70

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

Piston ring	new mm	Wear limit mm
1st compression ring	0.120 … 0.160	0.175
2nd compression ring	0.020 … 0.090	0.115
Oil scraper ring	0.020… 0.090	0.115

Checking piston –  Using a micrometer (75 ... 100 mm), measure approx. 10 mm from the lower edge, perpendicular to the piston pin axis. l  Maximum deviation from nominal dimension: 0.05 mm. Nominal dimension → Chapter „Piston and cylinder dimensions“.

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

Installation position of pistons   Caution Do not damage the coating of the piston crown. If you intend to reinstall used pistons, mark the cylinder number on the piston crown using paint. Do not mark piston crown by means of centre punch, notch or the like. l  Installation position: Arrow -item 1- on piston crown points to pulley end.

Marking conrods –  Before removing, mark mating positions of conrods and conrod bearing caps with coloured pen -arrow-.   Note t  Only renew conrods as a complete set. t  Do not interchange conrod bearings.

Conrod installation position The larger contact shoulder on the conrod -arrows- faces towards the adjacent crankshaft bearing.   Note Illustration shows front pair of conrods.