Piston and conrod: dismantling and assembling — VW

VW
Polo
2003
Power unit
4 - Cyl. injection engine (2 valves, roller rocker fingers)
Edition
04.2012
Piston and conrod: dismantling and assembling
Note
Before carrying out any assembly work, it is necessary to lubricate points of support and sliding surfaces.
Piston
Checking
Fig.
Mark installation position and cylinder number
Arrow
on piston crown points to pulley end
Install using piston ring clamp
Piston pin
If difficult to remove, heat piston to 60 °C
Remove and install with 10-206
Spring washer
Conrod
Only renew as a set
Mark cylinder number
A
Assembly position: Marking
B
faces towards pulley end
Guided axially via piston
Halfshell bearing
note the fitting position.
Do not interchange used bearing shells
Insert bearing shells centrally
Check radial clearance with Plastigage: New: 0.020...0.061 mm Wear limit: 0.091 mm Do not rotate crankshaft when checking radial clearance
Cylinder block
Checking cylinder bores
Fig.
Piston and cylinder dimensions
Chapter
.
Conrod bearing cap
note the fitting position.
The caps only fit in one position and only on the appropriate con-rod, this is due to the breaking procedure (cracking) separating the cap from the conrod
Conrod bolt, tighten to 30 Nm +
1
/
4
turn (90 °)
renew
Oil threads and contact surface
To measure radial clearance tighten to 30 Nm but not further
Oil scraper ring
Carefully remove and install 3 part oil scraper rings by hand
“TOP”
faces towards piston crown
Checking ring gap
Fig.
Checking ring to groove clearance
Fig.
Compression rings
Offset gaps by 120 °
Remove and install piston rings with piston ring pliers
“TOP”
faces towards piston crown
Checking ring gap
Fig.
Checking ring to groove clearance
Fig.
Checking piston ring gap check gap
Push ring squarely from above down to approx. 15 mm from bottom end of cylinder. .
Piston ring
Wear limit
1. Compression rings
1.0 mm
2. Compression rings
1.0 mm
Oil scraper ring
1.0 mm
Checking ring to groove clearance
Clean groove before checking.
Piston ring
Wear limit
1. Compression rings
0.25 mm
2. Compression rings
0.15 mm
Oil scraper ring
0.15 mm
Checking pistons
Special tools and workshop equipment required
Micrometer 60.. 90 mm
Measure to approx. 10 mm from lower edge, 90 ° at right angles to piston pin axis. Deviations from nominal dimensions Max. 0.07 mm. Nominal dimension
Chapter
; Piston and cylinder dimensions
Checking cylinder bore diameters
Special tools and workshop equipment required
Internal dial gauge 50...100 mm
Measure bores at 3 locations in both directions
A
across the engine and
B
in line with crankshaft. Deviation from nominal dimension Max. 0.08 mm. Nominal dimension
Chapter
; Piston and cylinder dimensions
Note
Measuring the cylinder bores must not be done when the cylinder block is mounted on a repair stand with
Engine and gearbox support
VW 540
, as incorrect measurements would then be possible.