Four-wheel drive vehicles (Haldex coupling) (Brake system)

Brake test on single-axle dynamometer for four-wheel drive vehicles

The dynamometer drives the wheels of one axle in opposite directions to avoid the other axle being driven.

We recommend use of a brake dynamometer with controlled roller speed and a max. test speed of 6 km/h.

Failure to comply with the above specifications can lead to brake application (EDL control).

In such cases switch off engine and ignition for test purposes. Run engine briefly if necessary to build up sufficient vacuum for brake test.

If no four-wheel drive dynamometer is available, testing can also be performed using a conventional dynamometer.

• ‒ Drive vehicle forwards onto rollers.
• ‒ Switch off engine and wait 2 seconds.
• ‒ Perform brake test at front.
• ‒ Start engine and let it run for approx. 5 s to build up sufficient vacuum in brake servo.
• ‒ Drive vehicle forwards until rear wheels are positioned on rollers.
• ‒ Switch off engine and wait 2 seconds.
• ‒ Perform brake test at rear.

Engine must not run and ignition must not be switched on during test, as otherwise rear axle would be driven by Haldex coupling.