1997 AUDI A8 AHA ATQ Engines Valve Gear Service Manual

15-49

Intake side

Note:
The intake valves are installed in the cylinder
head at different angles.

3362 valve spring tool can be used in two different positions:
1 - Upper position for center valve
2 - Lower position for two outer valves
3 - Threaded holes on each side to take M6 x 25 bolts for mounting valve
spring tool to cylinder head.

- Attach 3362 valve spring tool to cylinder head using two bolts supplied
(as shown in figure).
- Screw VW653/3 pressure hose together with seal hand tight into spark
plug hole of relevant cylinder and apply constant pressure (at least 6
bar).
- Set position of valve spring tool for relevant valve and remove valve
spring using threaded spindle.
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15-50


- Remove valve stem oil seal using 3364 valve seat tool.

- Place plastic sleeve -A- on valve stem to prevent damage to new valve
stem oil seals.
- Lightly lubricate sealing lip with oil.
- Insert valve stem oil seal -B- (without oiling outside of seal) into 3365
seal driver and carefully slide onto valve guide.
- When installing new valve, lightly oil valve stem before installing.
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15-51

Valves, refacing

WARNING!

Valves must not be refaced by cutting or
grinding.
Only hand lapping is permitted.
Observe the WARNING regarding proper
disposal of sodium-filled exhaust valves
page 15
-44
.
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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.
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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.
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15-54

Minimum dimensions
Outer intake
valve Center intake
valve Exhaust valve
32.2 mm
(1.268 in.) 33.2 mm
(1.307 in.) 33.0 mm (1.299
in.)
The measured distance minus the minimum
dimension equals the maximum permissible
refacing dimension.

Example
Outer intake valve
Measured distance 33.0 mm (1.299
in.)
Minimum dimension - 32.2 mm (1.268
in.)
Maximum permissible refacing
dimension = 0.8 mm (0.031
in.)

Note:
If the measured distance is less than the
minimum dimension, repeat the measurement
with new valves, or replace the cylinder head.
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