SEAT Workshop Service and Repair Manuals

Piston and conrod - assembly overview

1 -

Bolt.

q

Replace

q	Oil threads and contact surface.

q	30 Nm + turn +90° further

2 -	Conrod bearing cap

q	Due to the cracking method used to separate the bearing cap from the conrod in manufacture, the caps only fit in one position and only on the appropriate conrod

q	Mark cylinder allocation in colour -B-

q	Fitting position: Marking -A- towards the pulley end

3 -	Bearing cap

q	Installation position → Fig.

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

q	Renew bearing shells worn down to base layer.

q	Note design: Upper bearing shell (towards piston) made of wear-resistant material. Distinguishing feature of new bearing shells: Black line on contact surface in area of joint

q	Check for secure seating.

4 -

Conrod

q	Renew as set only.

q	With industrially cracked conrod bearing cap

q	Separating parts of new conrod → Fig.

q	Mark cylinder allocation in colour -B-

q	Fitting position: Marking -A- towards the pulley end

q	Axial clearance: Wear limit: 0.37 mm

q	Measuring radial clearance → Chapter

5 -

Circlip

q

Replace

6 -	Piston pin

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

q	Remove and install with drift -VW 222 A-

7 -

Piston

q	with combustion chamber

q	Mark installation position and cylinder number → Fig.

q	check → Fig.

q	Install using piston ring clamp

q	Piston and cylinder dimensions → Chapter

q	Measuring cylinder bore → Fig.

q	Measuring piston projection at „TDC“ → Chapter

8 -	Piston rings

q	Compression rings

q	Offset gaps by 120°

q	Use piston ring pliers to remove and install

q	Fitting position: Marking „TOP“ or side with lettering faces towards piston crown

q	Measuring piston ring gap → Fig.

q	Measuring axial clearance → Fig.

9 -	Piston ring

q	Oil scraping ring

q	Offset gap 120° from bottom compression ring

q	Use piston ring pliers to remove and install

q	Measuring piston ring gap → Fig.

q	Measuring axial clearance → Fig.

Measuring piston ring gap –  Insert piston ring from above at right angles to the cylinder wall to a depth of approx. 15 mm away from the lower edge of the cylinder. –  To do so, use a piston without rings.

Piston ring	new mm	Wear limit mm
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

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

Piston ring	new mm	Wear limit mm
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 –  Using a micrometer (75 ... 100 mm), measure approx. 15 mm from the lower edge, perpendicular to the piston pin axis. l  Maximum deviation from the nominal dimension: 0.04 mm. Nominal dimension → Chapter „Piston and cylinder dimensions“.   Note If piston skirt is cracked, renew piston.

Installation position of pistons and allocation of piston/cylinder l  Arrow on piston crown points to pulley end -arrows-.

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 the nominal dimension: 0.10 mm. Nominal dimension → Chapter „Piston and cylinder dimensions“.

Installation position of bearing shells in conrods –  Centre bearing shells on conrod and on conrod bearing cap. l  Dimension -a- = 2.5 mm

New conrod: Separate It is possible that the two parts of a new conrod are not completely separated as intended. Proceed as follows if the conrod bearing cap cannot be removed by hand: –  To avoid any risk of damage, the conrod should only be clamped lightly in a vice using jaw covers as shown in illustration. l  The conrod is clamped in position below the dotted line. –  Unscrew bolts -arrows- approx. 5 turns.

–  Loosen the head of the bearing cap -arrow- by knocking it gently with a plastic hammer.

Oil jets and pressure release valve 1 -  Bolt with pressure relief valve -27 Nm 2 -  Oil spray jet (for cooling of pistons) l  Fitting position: Align locating edge of oil spray jet with machined surface of cylinder block.   Note t  Do not bend oil spray jets. t  Renew bent oil spray jets.