Volkswagen Golf Service & Repair Manual: Checking for leaks

Volkswagen Golf Service & Repair Manual / Brake system / Brakes, hydraulics, regulator, servo / Vacuum system / 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-.

–	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).

Checking for leaks

–	Open cut-off valve -C- to evacuate brake servo.

–	Switch off engine.

–	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 ...

1 -	Brake servo

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:

Checking for leaks

–	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:

Checking for leaks

–	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.

Checking for leaks

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 increases (approx. 100 mb ...

Vacuum generation with manual vacuum pump -VAS 6213-

In certain cases, vacuum can be generated with the manual vacuum pump -VAS 6213- instead of with the engine or the vacuum pump. – ...

Other materials:

Checking inner constant velocity joint
The joint is to be dismantled to renew the grease if it is heavily soiled, or to check the running surfaces of the balls for wear and damage. Note The ball hub and joint body are paired. Mark position in relation to each o ...

Overview of fitting locations - operating and display unit, air conditioning system with electric/manual controls
Note A warning lamp in the instrument panel controls will indicate that the selected function is active. If the warning lamp does not light up after the AC button is pressed, a fault may be stored in the control ...

Checking the electrolyte level of the vehicle battery
Fig. 197 Engine compartment: pushing up the vehicle battery sleeve First read and observe the introductory information and safety warnings The electrolyte level of the vehicle battery should be checked regularly in high-mileage vehicles, in hot countries and in older vehicle batteries. T ...