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

15-1


Valve gear, servicing

WARNING!

Do not re-use any fasteners that are worn or
deformed in normal use.
Some fasteners are designed to be used only
once, and are unreliable and may fail if used
a second time. This includes, but is not
limited to, nuts, bolts, washers, circlips and
cotter pins. Always follow the
recommendations in this manual-replace
these fasteners with new parts where
indicated, and any other time it is deemed
necessary by inspection.

CAUTION!

After installing new hydraulic valve lifters the
engine must not be started for about 30
minutes (otherwise the valves will strike the
pistons). Turn the crankshaft two complete
revolutions by hand before starting.
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15-19

- Place VAG1306 drip tray beneath engine.

- Open engine coolant expansion tank cap.

WARNING!

The cooling system is pressurized when the
engine is warm. When opening the expansion
tank, wear gloves and other appropriate
protection, cover the cap with a cloth and
open carefully to relieve system pressure
slowly.

- With bumper removed, open coolant drain plug (arrow) on lower left of
radiator by turning it counterclockwise. If necessary, attach accessory
hose to connection.
- With bumper installed, pull off retaining clamp for lower right radiator
hose (from radiator to engine) and disconnect radiator hose from
radiator.

- Using 3247 hex ball socket, open coolant drain plug on engine (arrow)
as well.
- Unbolt engine coolant expansion tank from bracket and lay aside
(remove if necessary).
-
Disconnect crankshaft housing ventilation line from cylinder head
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15-43


Valve dimensions

WARNING!
Valves must not be refaced by cutting or grinding.Only hand lapping is permitted.Dimension
Intake valve
Exhaust valve
Diameter -a- 26.8 - 27.0 mm
(1.055 - 1.063 in.) 29.8 - 30.0 mm
(1.173 - 1.181 in.)
Diameter -b- 5.96 - 5.97 mm
(.2346 - .2350 in.) 5.94 - 5.95 mm
(.2338 - .2342 in.)
Length -c- 104.84 - 105.34 mm
(4.1275 - 4.1472 in.) 103.64 - 104.14 mm
(4.0803 - 4.0999 in.)
Angle -a-
45
45
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15-44

WARNING!

Sodium-filled exhaust valves must not be
scrapped without first being properly treated.
The valves must be cut open using a
hacksaw, by hand, between the valve head
and the middle of the stem.
The valves must not come into any contact
with water while being cut.
After cutting open the valves, throw not more
than 10 at a time into a bucket of water and
step back. A sudden chemical reaction will
occur during which the sodium filling is
consumed.
Valves that have been treated in this way can
be disposed of as normal waste.
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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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