Audi TT (2007 year). Manual — part 22
Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not
permitted unless authorised by AUDI AG. AUDI AG does not guarantee or accept any liability
with respect to the correctness of information in this document. Copyright by AUDI AG.
Measuring ring-to-groove clearance
– Clean groove in piston before checking clearance.
Piston ring
new
mm
Wear limit
mm
1st compression ring
0.06 … 0.09
0.25
2nd compression ring
0.05 … 0.08
0.25
Oil scraper ring
0.03 … 0.06
0.15
Checking piston
– Using a micrometer (75 ... 100 mm), measure approx. 15 mm
from the lower edge, perpendicular to the piston pin axis.
• Maximum deviation from nominal dimension: 0.04 mm.
Nominal dimension
⇒ “4.3 Piston and cylinder dimensions”, page 82
Note
Renew piston if cracking is visible on piston skirt.
Installation position of pistons and allocation of piston/cylinder
• 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-.
• Maximum deviation from nominal dimension: 0.10 mm.
Nominal dimension
⇒ “4.3 Piston and cylinder dimensions”, page 82
4. Pistons and conrods
79
Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not
permitted unless authorised by AUDI AG. AUDI AG does not guarantee or accept any liability
with respect to the correctness of information in this document. Copyright by AUDI AG.
Installation position of bearing shells in conrods
1 - Bearing shell with oil drilling -arrow- for conrod.
2 - Bearing shell without oil drilling for conrod bearing cap.
– Position bearing shells in centre of conrod and conrod bearing
cap when fitting.
• Distance -a- is the same on both sides.
Separating parts of new conrod
It is possible that the two parts of a new conrod are not completely
separated as intended. If it is not possible to take off the conrod
bearing cap by hand, proceed as follows:
– To avoid any risk of damage, the conrod should only be clam‐
ped lightly in a vice using jaw covers as shown in illustration.
• The conrod is clamped in position below the dotted line.
– Unscrew bolts -arrows- approx. 5 turns.
– Using a plastic hammer, carefully knock conrod bearing cap
loose -arrow-.
Oil spray jet and pressure relief valve
1 - Bolt with pressure relief valve, 27 Nm
2 - Oil spray jet (for cooling of pistons)
• Installation position: align locating edge of oil spray jet with
machined surface of cylinder block.
Note
♦
Take care not to bend oil spray jets.
♦
Always renew bent oil spray jets.
80
Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not
permitted unless authorised by AUDI AG. AUDI AG does not guarantee or accept any liability
with respect to the correctness of information in this document. Copyright by AUDI AG.
4.2
Measuring piston projection at “TDC”
Note
♦
Piston projection at “TDC” must be measured when installing
new pistons or a short engine.
♦
If the measured values for piston projection are not the same
for all pistons, use the highest value to determine the correct
gasket size.
♦
Depending upon piston projection, install the corresponding
cylinder head gasket according to the table below.
Special tools and workshop
equipment required
♦ Measuring bridge -
VW 382/7- from measuring
tool -VW 382-
♦ Measuring plate -
VW 385/17- from universal
measuring tool -VW 385-
♦ Dial gauge -VAS 6079-
4. Pistons and conrods
81
Protected by copyright. Copying for private or commercial purposes, in part or in whole, is not
permitted unless authorised by AUDI AG. AUDI AG does not guarantee or accept any liability
with respect to the correctness of information in this document. Copyright by AUDI AG.
Procedure
– Secure dial gauge -VAS 6079- with measuring bridge -
VW 382/7- and measuring plate -VW 385/17- to cylinder block
as shown in illustration.
– Measure piston projection at two points marked with
-arrows- for each piston.
Piston projection above top sur‐
face of cylinder block
mm
Identification
(No. of holes)
0.91 … 1.00
1
1.01 … 1.10
2
1.11 … 1.20
3
Identification of cylinder head gasket
1 - Part number
2 - Holes
3 - Ignore
Note
If the measured values for piston projection are not the same for
all pistons, use the highest value to determine the correct gasket
size.
4.3
Piston and cylinder dimensions
Honing dimension
Piston ∅
mm
Cylinder bore ∅
mm
Basic dimension
80.96
1)
81.01
•
1)
Dimensions including coating (thickness 0.02 mm). The
coating will wear down in service.
4.4
Measuring radial clearance of conrods
Special tools and workshop equipment required
♦ Plastigage
Procedure
– Remove conrod bearing cap. Clean bearing cap and bearing
journal.
– Place a length of Plastigage corresponding to the width of the
bearing on the bearing journal or in the bearing shell.
82
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