seats AUDI A4 1999 B5 / 1.G AWM Engine Valve Gear Service Workshop Manual

15-37


Valve gear, servicing

Note:

Cylinder heads that have cracks between the
valve seats or between valve seat inserts and
the spark plug thread can be used further
without reducing service life, provided the
cracks do not exceed a maximum of 0.3 mm in
width, or when no more than the first 4 turns of
the spark plug threads are cracked.
Wait about 30 minutes after installing the
camshafts before starting the engine. Hydraulic
valve compensation elements have to settle
(otherwise valves will strike pistons).
After working on the valve gear, turn the engine
carefully at least 2 rotations to ensure that none
of the valves make contact when the starter is
operated.
Replace all gaskets and seals.
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15-39


4 -
Cylinder head
See note Page 15
-37
Checking valve guides Page 15
-86
Reworking valve seats Page 15
-88
Dowel sleeves for bearing caps must be
located in cylinder head. Seal joints Fig. 3
and Fig. 4
,
Page 15
-8
5 -
Valve guide
Checking Page 15
-86
6 -
Valve stem seal
Replacing Page 15
-77
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15-45


22 -
Exhaust valve
With sodium fillingNote instructions on scrapping valves with
a sodium filling Page 15
-47

Do not rework, only lapping in is permittedValve dimensions Fig. 1
, Page 15
-
47

Checking valve guides Page 15
-86
Reworking valve seats Page 15
-88
23 -
Intake valve
Do not rework, only lapping in is permittedValve dimensions Fig. 1
, Page 15
-
47

Checking valve guides Page 15
-86
Reworking valve seats Page 15
-88Pa
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15-88

Valve seats, reworking


Note:
If a good seating pattern cannot be obtained by
grinding the valve seats (lapping), they must be
refaced (reworked):

Special tools and equipment

Depth gauge
Valve seat machining tool

Note:
When repairing engines with leaking valves, it is
not sufficient to reface the valve seats and
replace the valves. The valve guides must also
be checked for wear. This is particularly
important on high mileage engines Page 15
-
86
.

Only rework the valve seats as far as is
necessary to ensure a good seating pattern.
Before starting to rework the valve seats,
calculate the maximum permissible reworking
dimension.
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15-91


Rework valve seats Dim.

Intake valve seat
Dia. a mm 26.2
b mm 1.5 to 1.8
Z Lower edge of cylinder head

45
Valve seat angle

30
Upper correction angle

60
Lower correction angle
Dim.

Exhaust valve seat
Dia. a mm 29.0
b mm 1.8
Z Lower edge of cylinder head

45
Valve seat angle

30
Upper correction angle

60
Lower correction angle
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