AUDI TT 1995 8N / 1.G AEB ATW Engines Valvetrain Servicing Workshop Manual

15-32


Valvetrain, servicing

Note:

Cylinder heads with small cracks between the
valve seats that are less than 0.3 mm (0.012
in.) wide and/or between one valve seat and
only the first 4 threads of the spark plug thread,
can continue to be used without reduced
service life.
Always replace gaskets, seals and O-rings.

CAUTION!
After installing the camshafts, the engine
must not be started for approx. 30 minutes.
The hydraulic valve lifters have to settle
(otherwise valves will strike the pistons).
After installing the valvetrain and lifters,
carefully rotate the crankshaft by hand at
least 2 full revolutions before starting to be
sure that valves do not strike the pistons.
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1 -
Bolt
65 Nm (48 ft lb)Use 3036 retainer when loosening or
tightening
2 -
Camshaft gear For exhaust camshaftVerify correct installation position: thin rib
of camshaft gear points forward and TDC
Cyl. 1 marking is visible from front Page 15
-45

3 -
Oil seal
For exhaust camshaftAlways replace Page 15
-42
4 -
Cylinder head
Note Page 15
-32
Check valve guides, reface valve seats
Page 15
-66

Bearing cap bushings must be installed in
cylinder head Seal contact surfaces Page 15
-9 , Fig.
3
and Fig. 4

Reface valve seats Page 15
-71
5 -
Valve guide
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Check Page 15
-66
Replace Page 15
-67
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6 -
Valve stem oil seal
Replace Page 15
-62
7 -
Valve spring
Removing and installing Page 15
-62
8 -
Valve spring retainer
9 -
Valve keeper
10 -
Hydraulic valve lifter
Check Page 15
-60
Removing and installing Page 15
-62
Do not interchangeWhen removed, store with contact surfaces
facing down Before installing, check axial play in
camshafts Page 15
-41

Oil contact surface
11 -
Intake camshaft Using Plastigage check radial play (valve
lifters removed)
Wear range: 0.1 mm (0.004 in.)
Max. run-out: 0.01 mm (0.0004 in.)Axial play, checking Page 15
-41Pa
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Camshafts, removing and installing
Page 15
-50

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12 -
Bearing cap for intake camshaft
Must fit on bushingBushings must be installed in cylinder headVerify correct installation positionInstallation sequence Page 15
-50
13 -
Double bearing cap
Must fit on bushingBushings must be installed in cylinder headBefore installing, seal contact surfaces
lightly with sealant D 454 300 A2 Page 15
-57

Sealing contact surfaces between double
bearing cap and cylinder head Page 15
-
9 , Fig. 3

14 -
Exhaust camshaft
Using Plastigage check radial play (valve
lifters removed)
Wear range: 0.1 mm (0.004 in.)
Max. run-out: 0.01 mm (0.0004 in.)Axial play, checking Page 15
-41
Camshafts, removing and installing
Page 15
-50

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15 -
Bearing cap for exhaust camshaft
Must fit on bushingBushings must be installed in cylinder headVerify correct installation positionInstallation sequence Page 15
-50
16 -
Bolt
10 Nm (7 ft lb)
17 -
Bolt 10 Nm (7 ft lb)
18 -
Drive chain Check for wearBefore removing, mark installed position
Page 15
-52

Camshafts, removing and installing
Page 15
-50

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19 -
Hydraulic chain tensioner
Before removing, secure with VAG3366
chain tensioner bracket Removing and installing Page 15
-50
Seal contact surfaces between hydraulic
chain tensioner and cylinder head Page 15
-9 , Fig. 4

20 -
Rubber/metal seal
Replacing Page 15
-53
21 -
Gasket
Always replace
22 -
Exhaust valve Sodium-filledFollow disposal procedures for sodium-
filled valves Page 15
-40

Do not reface by grinding, only hand
lapping is permitted Valve dimensions Page 15
-39
, Fig. 1
Checking valve guides Page 15
-66
Refacing valve seats Page 15
-71Pa
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23 -
Intake valve
Do not reface by grinding; only hand
lapping is allowed Valve dimensions Page 15
-39
, Fig. 1
Checking valve guides Page 15
-66
Refacing valve seats Page 15
-71
24 -
Oil seal
For intake camshaftReplacing Page 15
-42
25 -
Shutter wheel for Camshaft Position
(CMP) sensor -G40-
Note position: insert lug in camshaft notch
26 -
Washer ConicalNote position
27 -
Bolt 25 Nm (18 ft lb)
28 -
Camshaft Position (CMP) sensor -G40-
housing
29 -
Bolt 10 Nm (7 ft lb)
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WARNING! Fig. 1 Valve dimensions
Valves must not be refaced by cutting or grinding.Only hand lapping is permitted.Dimension
Intake valve
Exhaust valve
Diameter -a-
mm
(in.) 26.80-27.00(1.055-
1.063) 29.80-30.00(1.173-
1.181)
Diameter -b-
mm
(in.) 5.95-5.97
(0.2339-0.2350) 5.94-5.95
(0.2339-0.2343)
Length -c- mm
(in.) 104.84-105.34
(4.127-4.147) 103.64-104.14
(4.080-4.099)
Angle -a-

45
45
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