seats AUDI A8 1998 D2 / 1.G AHA ATQ Engines Valve Gear Service Manual

15-2

Notes:

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 four threads of the spark plug
thread, can continue to be used without
reduced service life.
Carefully apply a small amount of sealant D 454
300 A2 at the four end points of the sealing
surfaces on the cylinder head using a small
screwdriver page 15
-13
.

CAUTION!

Part numbers are listed here for reference
only. Always check with your Parts
department for the latest information.
Pa
ge 2 of 62 Valve
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pair&id=AUDI.B5.GE03.15.1

15-52

Valve guides, checking

When servicing engines or cylinder heads with
leaking valves, refacing or replacing valve seats
and valves is not sufficient. Valve guides must be
checked for wear. This is especially important for
engines with high mileage.

Wear limit - Insert valve into guide.
Valve shaft edge must seal with guide. Due to differences in valve stem
diameter, make sure only intake valves are used to check intake
guides, and only exhaust valves are used to check exhaust guides.
- Measure axial play.Intake valve guide
Exhaust valve guide
0.8 mm (0.031 in.) 0.8 mm (0.031 in.) - If wear limit is exceeded, replace cylinder head.
Pa
ge 60 of 62 Valve
gear, servicin
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11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
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pair&id=AUDI.B5.GE03.15.1

15-53

Valve seats, refacing


Notes:

Only reface valve seats enough until a perfect
contact pattern is obtained.
Before refacing, calculate the maximum
refacing dimension.
If refaced dimension is exceeded, hydraulic
valve lifter function is no longer guaranteed and
cylinder head must be replaced.

Calculating maximum allowable refacing
dimension

- Insert valve and press firmly against valve
seat.

Note:
If valve is replaced during repair, use a new
valve for measurement.

- Measure distance between end of valve stem and top surface of
cylinder head (four-valve head shown).
- Calculate maximum allowable refacing dimension using distance
measured and minimum dimension.
Pa
ge 61 of 62 Valve
gear, servicin
g
11/21/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.GE03.15.1