SEAT Workshop Service and Repair Manuals > Leon Mk1 > Running gear | Brake system: | Brakes, hydraulics, regulator, servo | Assembly overview: Brake servo / Master brake cylinder

Checking for leaks

Note

t	The average earth atmospheric pressure at sea level is 1.013 mbar and falls the higher you travel (approx. 100 mbar / 1,000 m height). The regional and periodic deviations also influence the vacuum.

t	A cold engine, an air conditioner compressor switched on as well as an idling engine have a negative influence on the vacuum.

–	Visually inspect all vacuum hose for damage (e.g. cracks or vermin bites - in some countries) and their tight fit in advance.

–	Connect the Brake servo tester -VAS 6721- → Chapter.

–	Open the shut-off valve -A-.

–	Close the shut-off valves -B and C-.

–	Start the engine at operating temperature (> 60° C), press the accelerator briefly once (engine speed more than 2.000 rpm).

Normally (see note), the vacuum generated is between 600 and 950 mbar, depending on the engine power output.

–	Open shut-off valve -C- in order to drain the brake servo.

–	Switch off the engine.

–	Read off and note the measuring value displayed.

The vacuum may sink by 400 mbar in 12 hours.

With greater reductions in pressure, a check should be made if leaks in the vicinity of the

1 -	brake servo

or the

2 -	shut-off valve, the the vacuum hose connections and the hand vacuum pump / the intake tube are at hand.

With greater leaks, the vacuum falls quickly within a few seconds.

Vacuum test in the area of the brake servo:

–	Shut-off valve -A- must be closed after generating a vacuum so that the vacuum system of the brake servo can be checked.

Vacuum test in the area of the shut-off valve, the the vacuum hoses with connections and the hand vacuum pump / the intake tube.

–	The shut-off valve -A- must be closed after generating a vacuum so that the vacuum system can be checked from the Brake servo tester -VAS 6721- to the hand vacuum pump or intake tube.

In order to make removing the hose connections and the adapter easier, open the shut-off valve -B-.

SEAT Workshop Service and Repair Manuals