seats AUDI A4 1998 B5 / 1.G APB Engine Valve Gear Service Workshop Manual

15-1


Valve gear, servicing

Notes:

Cylinder heads which have cracks between the
valve seats or between valve seat inserts and
the spark plug thread can be used further
without reducing service life, provided the
cracks do not exceed a maximum of 0.3 mm in
width, or when no more than the first 4 turns of
the spark plug threads are cracked.
After installing new lifters the engine must not
be started for about 30 minutes (otherwise
valves will strike pistons). Turn crankshaft two
complete revolutions before starting.
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 Fig. 1
.
Pa
ge 1 of 99 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.GE05.15.1

15-95

Valve guides, checking

When repairing engines or cylinder heads 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.

Wear limit
If the wear limit is exceeded, replace cylinder head. - Insert valve into valve guide so that end of valve stem is flush with end
of guide. The valve stems have different diameters, so only use an inlet
valve in an inlet guide and an exhaust valve in an exhaust guide.
- Measure amount of rock. Inlet valve guide
Exhaust valve guide
0.8 mm 0.8 mm
Pa
ge 96 of 99 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.GE05.15.1

15-96

Valve seats, reworking (refacing)


Notes:

The valve seats should only be reworked just
enough to produce a good seating pattern.
Calculate the maximum permissible reworking
dimension before reworking.
If the reworking dimension is exceeded, the
function of the hydraulic lifters can no longer be
guaranteed and the cylinder head should be
replaced.

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 between end of valve stem and top surface of
cylinder head (illustration shows a 4-valve head).
-
Calculate maximum permissible reworking dimension from measured
Pa
ge 97 of 99 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.GE05.15.1