Parking Brake faiulure

[Ac505]

Hi all, The parking brake failed to release on our X5 this evening. I had to use the brake tool in the boot to release the brakes in order to get home. At least I know the parking brake worked well.....

Anyway, I'm covered via a warranty policy so all should be okay, however I'm curious as to whether or not this is a common fault and if common, what the repair procedure is?

[X5Sport]

Was the actuator making any noise?  If not then it might just be a fuse.

Richard

[martin33100]

[quote="X5Sport"]
Was the actuator making any noise?  If not then it might just be a fuse.

Richard
[/quote]How do these brake's work?, ie does the actuator put on the brake or is it sprung loaded on ie the actuator is holding it off while you drive.

[X5Sport]

Straight from the BMW Tech manual......

The parking brake (EMF) has two different functions, depending on the operating status of the vehicle.

• Parking brake mode
– When the engine is running or the vehicle is rolling, the parking brake acts on the service brake with the aid of the DSC hydraulics. This means the brake units on the front and rear axle are active.
– If the engine is not running and the vehicle is stationary, the electromechanical actuator and its cable assembly ensure the parking brake acts on the duo-servo drum brake on the rear axle. In this case, the vehicle is braked as defined in the control unit.

• Dynamic braking
Defined retardation is triggered via the DSC system if the parking brake button is pulled up while driving. The retardation or deceleration is monitored by the DSC control functions and takes place for as long as the parking brake button is pulled.

Emergency Release

A mechanical emergency release facility is provided in order to be able to release the parking brake in the event of the electromechanical actuating unit failing or insufficient power supply.
Warning!  Secure vehicle to prevent it rolling before operating the emergency release!

The release procedure is performed manually with the emergency release cable assembly and the emergency release handle from the vehicle tool kit. The emergency release procedure releases the duo-servo drum brake by way of mechanical intervention in the actuator of the electromechanical control unit.

Note: After a power failure, it may still not be possible to move the vehicle even after releasing the brake with the emergency release facility. The parking lock of the automatic gearbox may still be engaged (see Product Information Automatic Gearbox E70).

Once released, using the emergency release facility, the parking brake cannot be reactivated manually. The function can be restored only by way of electrical activation.

Restoring Operation After Emergency Release

After turning on the ignition, push down the EMF operating button and pull up again to activate the parking brake.