Volkswagen Golf Service & Repair Manual: Checking for leaks
 Note
| The average air pressure of the earth's atmosphere at sea
level is 1013 mbar and decreases steeply as the altitude
increases (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-
→ Chapter. |
| – |
Open cut-off valve -A-. |
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Close cut-off valves -B+C-. |
| – |
Start warm engine (>60°C), press accelerator briefly (engine
speed above 2,000 rpm). |
| Normally (see notes), the vacuum that is generated should be
between 600 and 950 mbar (depending on engine size). |
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Open cut-off valve -C- to
evacuate brake servo. |
| – |
Read and make a note of measured value shown. |
| A vacuum decrease of 400 mbar in 12 hours is permissible. |
| If the vacuum decrease is greater, check for leaks in the
vicinity of ... |
| 2 - |
Non-return valve of vacuum hoses with connectors and vacuum
pump/suction pipe. |
| If there are large leaks, the vacuum decreases steeply
within a few seconds. |
| Vacuum check in vicinity of brake servo: |
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| – |
After generation of vacuum, close cut-off valve
-A- to check brake servo vacuum
system. |
| Vacuum check in vicinity of non-return valve, vacuum hoses
with connectors and vacuum pump or intake manifold: |
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| – |
Once vacuum has been generated, close shut-off valve
-C- to check vacuum system from
brake servo vacuum gauge -VAS 6721- to intake manifold or to
vacuum pump. |
| Open cut-off valve -B- to
facilitate removal of hose connections and adapter. |
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Note
The average air pressure of the earth's atmosphere at sea
level is 1013 mbar and decreases steeply as the altitude
increases (approx. 100 mb ...
In certain cases, vacuum can be generated with the manual
vacuum pump -VAS 6213- instead of with the engine or the vacuum
pump.
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Checking vacuum generation
Vacuum generation with manual vacuum pump -VAS 6213-