seats AUDI A4 1999 B5 / 1.G AFC Engine Lock Carrier Removing For Service Workshop Manual

15-29

Valve guides, checking and replacing


Checking
When repairing engines with low compression
due to leaking valves, it is not sufficient to reface
or replace the valve seats and valves. It is also
necessary to check the valve guides for wear.
This is particularly important when checking
engines with high mileage.

- Insert new valve into guide until end of valve
stem is flush with end of guide.

CAUTION!

Due to the difference in valve stem diameters,
make sure that only an intake valve is used to
check intake valve guides, and that only an
exhaust valve is used to check the exhaust
valve guides.

Wear limit - Determine valve rock-amount that valve can move side-to-side.
Intake valve guide 1.0 mm (0.039 in.)Exhaust valve guide 1.3 mm (0.051 in.)
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15-30

Replacing

CAUTION!

Cylinder heads with valve seats that can no
longer be refaced, or which have already
been machined to the minimum dimension,
should no longer be repaired.

CAUTION!
When the shoulder on the new guide makes contact, the pressing
force must not exceed 1.0 ton or the guide shoulder could break off. - Press out worn valve guides from camshaft side using drift 10-206.
(Replacement guides with shoulder must be pressed out from
combustion chamber side.)
- Coat new guides with oil and, using drift 3121, press into cold cylinder
head from camshaft side until shoulder makes contact.
- Use 7mm reamer 3120 to ream new valve guides to size, using plenty
of cutting fluid.
Pa
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15-31

Valve seats, refacing


Note:

Pay attention to the cylinder head minimum
dimension when refacing valve seats page 15
-32


Only reface valve seats enough to produce
perfect contact.
Before refacing, calculate the maximum
permissible refacing dimension. If this
dimension is exceeded, correct functioning of
hydraulic valve lifters can no longer be
guaranteed and the cylinder head must be
replaced.

Intake valve seat
a - Diameter: 39.2 mm (1.543 in.)
b - Max. permissible refacing dimension
1)
c - Seat width: 2.0 mm (0.079 in.)
30 - Upper correction angle 45 - Valve seat angleZ - Bottom surface of cylinder head
Pa
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