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– Push hose -A- of brake servo vacuum gauge -VAS 6721- onto
vacuum hose and press adapter -C- into brake servo.
6.4.2
Checking vacuum generation
Note
♦
The average air pressure of the earth's atmosphere at sea
level is 1013 mbar and decreases steeply as the altitude in‐
creases (approx. 100 mbar/1,000 m altitude). Local and time
fluctuations also influence vacuum generation.
♦
A cold engine, a switched-on air-conditioning system as well
as engine idling have an adverse influence on generation of a
vacuum.
– Before starting work, check all vacuum hoses for damage (e.g.
cracks or marten bite) and to check that they are correctly and
firmly attached
– Connect brake servo vacuum gauge -VAS 6721-
– Open cut-off valve -A-.
– Close cut-off valves -B+C-.
– Start warm engine (>60° C), press accelerator briefly (engine
speed greater than 2000/min).
– Read indicated measured value.
Normally (see notes), the vacuum that is generated should be
between 600 and 950 mbar (depending on engine size).
If the measured value is not reached even through the precondi‐
tions (see notes) have been met, the vacuum system must first
be checked for leaks.
– For comparison purposes, generate the vacuum with the man‐
.
Open cut-off valve -B- to facilitate removal of hose connections
and adapter.
Touareg 2010 ➤
Brake systems - Edition 05.2011
88
Rep. gr.47 - Brakes - hydraulics
