SEAT Workshop Service and Repair Manuals

Piston and conrod - General components overview

1 -	Conrod bolt - 30 Nm +90° (1/4 turn) further

q

Replace.

q	Oil threads and contact surface.

q	To measure the radial play, use used bolts

2 -	Conrod bearing cap

q	Mark cylinder number -B-

q	Fitting position: The marks -A- should point towards the pulley

3 -	Bearing shell

q	Installation position → Fig.

q	Do not interchange used bearing shells (mark).

q	Note design: Upper half-bearing (to piston) made from more resistant material. Distinguishing factors with new bearing shells: Black line on the contact surface in the cutting area

q	Check for secure seating.

q	Axial play, wear limit: 0.37 mm

q	Check radial clearance with Plastigage

q	When measuring the radial play, do not rotate the crankshaft

q	Radial play; wear limit: 0.08 mm

4 -

Conrod

q	Renew as set only.

q	Mark cylinder number -B-

q	Fitting position: The marks -A- should point towards the pulley

5 -	Securing ring

6 -	Piston pin

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

q	Removing and installing with the awl -T20019-

7 -

Piston

q	With combustion chamber

q	Mark the installation position and the cylinder correspondence

q	Installation position and piston/cylinder correspondence → Fig.

q	Arrow on piston crown points to pulley end

q	If the piston is scratched, replace it

q	Checking piston → Fig.

q	Piston and cylinder dimensions → Chapter

q	Checking cylinder bore → Fig.

q	Install using piston ring clamp

q	Checking piston position at TDC → Chapter

8 -	Piston rings

q	Compression rings

q	Displace the gaps at 120° from each other

q	Use piston ring pliers to remove and install

q	“TOP” must face towards piston crown

q	Piston ring ends: check clearance → Fig.

q	Check play with piston groove → Fig.

9 -	Piston ring

q	Oil scraping ring

q	Displace the gaps by 120° towards the lower compression ring

q	Use piston ring pliers to remove and install

q	Piston ring ends: check clearance → Fig.

q	Check play with piston groove → Fig.

Checking piston ring gap –  Push ring squarely from above down to approx. 15 mm from bottom end of cylinder. For insertion, there must be no segments on the piston.

Piston ring (Dimensions in mm)	New	Wear limit
1. Compression ring	0,20 … 0,40	1,00
2. Compression ring	0,20 … 0,40	1,00
Oil scraping ring	0,25 … 0,50	1,00

Check play with piston groove –  Before the test, clean the neck for the piston ring.

Piston ring (Dimensions in mm)	New	Wear limit
1. Compression ring	0,06 … 0,09	0,25
2. Compression ring	0,05 … 0,08	0,25
Oil scraping ring	0,03 … 0,06	0,15

Checking pistons –  Measure about 10 mm from the lower edge, at 90 º to the axis of the piston pin. l  Maximum deviation from the nominal dimension: max. 0.04 mm

Installation position and piston/cylinder correspondence l  The arrow points to the cylinder 1 -arrows-.

Check bore –  Measure, with a precision interior gauge 50 … 100 mm at three different points across in a transversal -A- and longitudinal direction -B-. l  Maximum deviation from the nominal dimension: max. 0.10 mm

Installation position of the bearing shells in the conrods –  Fit the bearing shells centrally in the conrod or in the conrod bearing cap. l  Dimension a = 2.5 mm

Oil jets and pressure release valve 1 -  Bolt with pressure relief valve -27 Nm 2 -  Oil spray jet for cooling piston