Volkswagen Workshop Service and Repair Manuals

Dismantling and assembling pistons and conrods

1 -	Piston rings

q	Offset gaps by 120°.

q	Use piston ring pliers to remove and install

q	“TOP” faces towards piston crown.

q	Checking piston ring gap → Fig..

q	Checking ring-to-groove clearance → Fig..

q	2 or 3 part oil scraper ring, mixed installation permissible

2 -

Piston

q	Check → Fig..

q	Mark installation position and cylinder number.

q	Arrow on piston crown points to belt pulley end.

q	Install using piston ring clamp.

q	Characteristics → Fig.

3 -

Conrod

q	Renew as set only.

q	Mark cylinder number -B-.

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

q	For 85 kW engines with oil drilling for piston pin lubrication

4 -	Conrod bearing cap

q	Note installation position.

5 -	30 Nm + 1/4 turn (90 °) further

q	Oil threads and contact surface

q	To measure radial clearance, tighten to 30 Nm but do not turn further.

6 -	Pressure relief valve, 27 Nm

q	For 85 kW engines

q	Opening pressure: 2.5…3.2 bar

7 -	Oil spray jet

q	For 85 kW engines

q	For piston cooling.

8 -	Bearing shell

q	Note installation position.

q	Do not interchange used bearing shells

q	Ensure secure seating in retaining lugs

q	Axial clearance new: 0.05…0.31 mm , wear limit: 0.37 mm

q	Check radial clearance with Plastigage: new = 0.01…0.06 mm; wear limit = 0.12 mm. Do not rotate crankshaft when checking radial clearance.

9 -	Cylinder block

q	Checking cylinder bore → Fig..

q	Piston and cylinder dimensions → Chapter.

10 -	Conrod bolt

11 -

Circlip

12 -	Piston pin

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

q	Remove and install using drift -VW 222 A-

Checking piston ring gap –  Insert ring at right angles from above and push down into cylinder approx. 15 mm from bottom end of cylinder.

Piston ring		Ring gap
		New	Wear limit
Compression rings	mm	0.20…0.40	1.0
Oil scraper ring	mm	0.25…0.50	1.0

Checking ring-to-groove clearance Clean annular groove before check.

Piston ring		Clearance
		New	Wear limit
Compression rings	mm	0.02…0.05	0.15
Oil scraper ring	mm	0.02…0.05	0.15

Checking piston Measure piston approx. 10 mm from lower edge of skirt, at 90° to piston pin axis. Deviation from nominal dimension max. 0.04 mm

Piston characteristics

Engine codes		AAM and ANN	ABS	ADZ and ANP
Dimension “a”	mm	22.2	22.2	22.2
Dimension “b”	mm	8.1	4.4	4.4
Recess Ø “c”	mm	56.8	56.0	56.0
Piston pin Ø “d”	mm	20.0	20.0	20.0

Engine codes		2E	ADY	AGG and AKR
Dimension “a”	mm	20.4	20.4	20.4
Dimension “b”	mm	5.0	5.0	5.7
Recess Ø “c”	mm	64.0	64.0	64.0
Piston pin Ø “d”	mm	21.0	21.0	21.0

When performing repairs, only pistons and piston rings of the same type and pistons in the same weight class must be installed in the engine.

Checking cylinder bores t  Take measurements at 3 positions in both lateral direction -A- and longitudinal direction -B-. t  Use cylinder gauge 50…100 mm. t  Deviation from nominal dimension max. 0.08 mm   Note Cylinder bores must not be measured when cylinder block is mounted on a repair stand with engine and gearbox support -VW 540-, as measurements may then be incorrect.