Parking brake - how to manual override.

[Marekdawg]

Hi All,

As the title suggests, I am having issues with my electric parking break.

Car was sat for a while and I didn't realise the Mrs had unknowingly unplugged the trickle charger so car was completely dead. Chucked a new battery in and everything is as it should be, all but the handbrake.
It is stuck on and wont release - now I have looked around and seems that there is no actual 'manual' release for this, it usually has to be done with BMW code reset. However, as I cant move the thing this poses an issue...
I have seen someone mention the ability to manually run the servo with a battery straight to the terminals of the parking brake - Anyone know if this is possible / how I would go about actually doing it?

Worth noting that I have 0 access to the rear left wheel, as its parked against the wall on that side so access will have to be from the rear and under...

 

[B21]

Parking brake is operated by the EPB ECU..but if the ECU is barfed then..

Normal way is to remove the electric motor from the back of the caliper..but you can't access LHS?

 

[Rockhopper]

Is it possible that that pads have rusted to the disc especially if the car was put away wet? A few taps with a hammer might be enough or just try and drive it out - some clutch dumpage might be needed.

 

[Matt.rowley.1990]

If you can get the car jacked up at the rear, you should be able to access the caliper's electrical connector.

With that off, you should be able to apply 12v to the two outer pins on the connector. Crocodile clips would be ideal for this.

You can see the two lager pins here in one of Peter's pictures. The middle pin is a sense line to indicate to the parking brake ECU the position of the piston in the caliper.

 

[RobbiZ4]

Is it possible that that pads have rusted to the disc especially if the car was put away wet? A few taps with a hammer might be enough or just try and drive it out - some clutch dumpage might be needed.

It's a well known software bug in the EPB module.

The software of the EPB module must be updated with ISTA/P, then it will be operational again. That's possible, even while it's in the garage.

 

[Marekdawg]

Thanks All,
Will try to see if its pads stuck as I can hear the servo trying to run, just not being successful.

If not, then I guess more research into the EPB module!

 

[B21]

Thanks All,
Will try to see if its pads stuck as I can hear the servo trying to run, just not being successful.

If not, then I guess more research into the EPB module!

If the EPB motors run then they will have released..and in that case the EPB ECU is probably not corrupted…

Ideally you need to plug a decent bmw specfic code reader in to see what gives..

If that’s the case it could be stuck pads…I washed my car a few days ago then parked it in my garage ..it took a very large amount of throttle to dislodged it..

 

[Rockhopper]

I’m aware of the software issue but I thought that just put the light on and stopped the parking brake from working?

 

[B21]

I’m aware of the software issue but I thought that just put the light on and stopped the parking brake from working?

Depends whether the EPB was applied or not at the time of the failure..most often happens after someone has parked up applied the EPB then the battery goes flat..good night Vienna

 

[Bombur]

Depends whether the EPB was applied or not at the time of the failure..most often happens after someone has parked up applied the EPB then the battery goes flat..good night Vienna

Is it best to store away the car with EPB off then?

 

[B21]

Is it best to store away the car with EPB off then?

Yup that’s a good move if you have an auto / DCT or leave it in gear for a manual…

Plus if you park the car wet with the EPB on it tends to weld the pads to the discs..

 

[Chippie]

It’s a few years ago that mine failed , but from memory, I got back in the car after it had been parked up for half an hour, started the engine disengaged the electric parking brake and then noticed the warning light on the dash, drove it home and the EPB wouldn’t then work, so I guess it’s just luck if it fails stuck on or off.

 

[Bombur]

Yup that’s a good move if you have an auto / DCT or leave it in gear for a manual…

Plus if you park the car wet with the EPB on it tends to weld the pads to the discs..

Will remember that next time, it's off sorn on Sunday is connected to a CTEK and worked fine a few weeks ago when I got it out for some tinkering. But the idea thats someone could knock off power to the charger has scared me haha, so will not engage the ESP next time it's put away for a while