check engine AUDI A6 1995 C5 / 2.G AEB ATW Engines Valvetrain Servicing Workshop Manual

15-60

Hydraulic valve lifters, checking


Special tools and equipment

Feeler gauge
Wood or plastic wedge

Note:
Hydraulic valve lifters cannot be serviced.
Irregular valve noise when starting engine is
normal.

- Start engine and let run until coolant
temperature reaches at least 80 C (176 F).

- Increase RPM to 2500 for about 2 minutes; if
necessary test drive vehicle.

Note:
If irregular valve noises disappear but then
reappear during drive, replace oil retaining valve.
Oil retaining valve is located in oil filter bracket
Page 17
-6 .
If hydraulic valve lifters are still loud, locate faulty
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15-71

Valve seats, refacing


Note:
If a perfect contact pattern isn't obtained after
hand lapping valves, reface valve seats.

Special tools and equipment

Depth gauge
Valve seat refacing tool

Note:
When servicing engines with low compression
due to leaking valves, it is not sufficient to
reface or replace the valve seats and valves. It
is especially important to check valve guides for
signs of wear on high-mileage engines Page 15
-66
.

Only reface valve seats enough until a perfect
contact pattern is obtained.
Before refacing, determine maximum refacing
dimension.
If refaced dimension is exceeded, hydraulic
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