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

15-85

- Install camshafts and camshaft adjuster Page
15
-67


Note:

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.
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15-86

Valve guides, checking


Special tools and equipment

Test sequence
Universal dial indicator bracket VW 387Dial indicator

Note:
Due to the slight difference in stem diameters, ensure that only an intake
valve is used in an intake guide and an exhaust valve in an exhaust
guide. - Set valve in guide. Valve stem end must be flush with guide.
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15-87

- Determine lateral play.

Wear limit

Intake valve guide
Exhaust valve guide
0.80 mm 0.80 mm

Note:

If the wear limit is exceeded, repeat the
measurement with new valves. Replace valve
guide if wear limit is still exceeded.
If the valve is to be replaced as part of a repair,
use a new valve for the calculation.
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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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If the maximum reworking dimension is
exceeded, the hydraulic lifters will not work
properly and the cylinder head will have to be
replaced.
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15-89

Calculating maximum permissible reworking
dimension

- Insert valve and press firmly against valve
seat.

Note:
If the valve is to be replaced as part of a repair,
use a new valve for the calculation.

- Measure distance -a- between valve stem end (upper edge) and upper
cylinder head surface -1- with a depth gauge.
- Calculate max. permissible reworking dimension from measured
distance and minimum dimension.
Minimum dimensions
Outer intake valves Central intake valve Exhaust valves
31.0 mm 32.2 mm 31.9 mm
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15-90
Measured distance minus minimum dimension =
max. permissible reworking dimension.

Example (for outer intake valve):
Measured distance 31.4 mm
- Minimum dimension -31.0 mm
= max. permissible
reworking dim. = 0.4 mm

Note:
If the maximum permissible reworking dimension
is 0 mm or less than 0 mm, repeat the
measurement with a new valve. If the measured
result is again 0 mm or less than 0 mm, replace
the cylinder head.
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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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