DIY Parking Brake Replacement

[Aveman]

I made a video on how to remove and install a parking brake module on an E70.

https://youtu.be/dzGiJWp3xHU

This video shows you had to replace the module with leaving the bowden cables on the car and removing it with the cables attached to the module.

Hopefully this helps a few people out. I bought a re-manufactured module off Ebay for $365 and fixed my problem. They use the later updated module made after 2011. The video shows you where I bought mine.

[08-730d]

Hello Aveman.
I´m the one from the comments on youtube.
I just installed the new item. I also put in new bowden cables and the entire brake shoe assembly.

I have a few questions before I put it into operation.

[IMG][/IMG]

It is a bit tighter with adaptive drive:

[IMG][/IMG]


Did you tighten the tensioner on the brake shoes when you reassembled your car? I wonder because both of the old units had the screw on the bowden cables bottomed out, and I think that may be at least a part of the reason why they broke:

[IMG][/IMG]

Do you have any thoughts about this?
(Anything else to check before I try to operate it?)

The old tensioner was not tensioned at all. Could this, coupled with a little stretched cables, and maybe a little worn shoes make the screw compress all the way and make the unit fail?

Thanks in advance..

[Aveman]

I did not make any changes to the adjuster on the brake shoes. The Bowden cable does not need to be bottomed out, my advise is back the cable out till it is about 3 or 4 turns in. Also reset the adjusters on the shoes to be on their loosest setting. The blue slidding thing with the ribbon cable is the force sensor and I doubt that the module would allow enough force to break anything. If you have your laptop setup you can monitor the force being measured by the sensor. What exactly happened with your first module and the first replacement module? Like what exactly broke?

To answer your last question I don't think the units fail due to requiring too much force to compensate for wear. I think they fail because the DC motor inside wears and the DC brushes get fouled and cause it to pull too much current (amps) and fry the control board inside. Or you run the car with very low voltage and burn out the control board.

[08-730d]

Thanks for the reply.
On the new unit I put the new bowden
cable just like it was, about 3,5cm from the tip of the threaded part of the unit to the black square on the screw, when pulled towards that side.
The picture of the bottomed out screw is the old unit. By the sound it (both) made when it (they) broke I would think the reason could be that the bowden cable screws bottomed out. I agree that it should not be possible, but that is the only thing similar between them (both screws in them were bottomed out). On the chinese replacement there was also some dark areas by the contacts:
[IMG][/IMG]

Other than that I haven´t found any faults on them yet.

My thought was not that it took more force due to wear, but that due to wear, the cables have to compress more, aka making the screw bottom out (making the motor reach its max torque peak..). I´m thinking that it can´t be good for it to bottom out the screw anyhow, as I´m thinking that it should be the brake being applied that stops the screw, not itself being bottomed out.
With the service kit included for the shoes, there was a little leaflet with instructions. It said to readjust the adjuster after changing the shoes according to bmws specifications..
I don´t have those specs, but I set the adjuster so that the park brake did not rub the brake disc.

Now all that is left is coding it.

[absentmathis]

Nice, could have really used this video myself a few months back. I ended up pulling my module, sending it to be rebuilt (including new Bowden cables) and reinstalling. Think it set me back $350 IIRC.

[Aveman]

Originally Posted by 08-730d

Thanks for the reply.
On the new unit I put the new bowden
cable just like it was, about 3,5cm from the tip of the threaded part of the unit to the black square on the screw, when pulled towards that side.
The picture of the bottomed out screw is the old unit. By the sound it (both) made when it (they) broke I would think the reason could be that the bowden cable screws bottomed out. I agree that it should not be possible, but that is the only thing similar between them (both screws in them were bottomed out). On the chinese replacement there was also some dark areas by the contacts:
[IMG][/IMG]

Other than that I haven´t found any faults on them yet.

My thought was not that it took more force due to wear, but that due to wear, the cables have to compress more, aka making the screw bottom out (making the motor reach its max torque peak..). I´m thinking that it can´t be good for it to bottom out the screw anyhow, as I´m thinking that it should be the brake being applied that stops the screw, not itself being bottomed out.
With the service kit included for the shoes, there was a little leaflet with instructions. It said to readjust the adjuster after changing the shoes according to bmws specifications..
I don´t have those specs, but I set the adjuster so that the park brake did not rub the brake disc.

Now all that is left is coding it.

I'm going off the top of my head here but you would back the drivers side screw all the way out, slide the complete mechanism toward the passenger (you could pull on the end of the passenger side cable) then screw in the black plastic screw connected to the driver side cable in about 4 turns. Then screw on the cap. This will put the mechanism in the loosest setting and allow full travel of the motor without binding.

[08-730d]

Originally Posted by absentmathis

Nice, could have really used this video myself a few months back. I ended up pulling my module, sending it to be rebuilt (including new Bowden cables) and reinstalling. Think it set me back $350 IIRC.

Where did you send it?
I was looking into that before I got a new unit, but did not find any who could do that at the moment.

[08-730d]

Originally Posted by Aveman

I'm going off the top of my head here but you would back the drivers side screw all the way out, slide the complete mechanism toward the passenger (you could pull on the end of the passenger side cable) then screw in the black plastic screw connected to the driver side cable in about 4 turns. Then screw on the cap. This will put the mechanism in the loosest setting and allow full travel of the motor without binding.

Yes, good point sir. I don´t think I´m far off this time.
But why did it happen in the first place..? (we can leave it at that for now..).

Hopefully I will get it right this time, as my car has an inspection coming up soon. Needs to pass it before I can put another coat of Fluid Film on the underside of the car before salt season starts again.

Anyway, I must say again that I really appreciate you making this diy video . Hopefully you´ll keep up the good work if you come across more x5 projects.

[Aveman]

Originally Posted by 08-730d

Yes, good point sir. I don´t think I´m far off this time.
But why did it happen in the first place..? (we can leave it at that for now..).

Hopefully I will get it right this time, as my car has an inspection coming up soon. Needs to pass it before I can put another coat of Fluid Film on the underside of the car before salt season starts again.

Anyway, I must say again that I really appreciate you making this diy video . Hopefully you´ll keep up the good work if you come across more x5 projects.

Yes it is puzzling as to what the root cause of your failure was, perhaps it's designed to compensate for cable stretch and brake shoe wear but depending on how you set it up in the first place it can run out of adjustment and lead to failure. You would think the force sensor would tell the module to stop before it could do any damage.

My pleasure, glad it helped. I will make more videos and other things come up.

[08-730d]

Well well. Looks like things are looking up at the moment. Got it coded today and adjusted the brake shoe tensioner. And now it seems to be fine. It just made sweet sounds (altough i haven´t dared to operate it more than once..).

I did also study the first unit that broke. Nothing looks to be burned, and it ran fine while putting power directly to the motor.
I also used it to measure, and found that the only thing I could have done better with the new one was to adjust the bowden cable screw 3mm further out, than it is (or 1,75 turns of the screw). In total the screw has about 50-55 mm of travel, and 3 mm should not make that big of a difference.
I also studied the bowden cable connection inside the brake disc. It looks to me that the ratio of how much the cable moves vs how much the brake shoes are moved is not in our favour. By that I mean that it looks like the cable has to move a lot more than what we get in brake shoe motion. Therefore I would presume that it would be beneficial for the operation of the park brake system to keep this movement as low as possible, by adjusting the brake shoe tensioner so that the brake shoes almost rub.

I don´t know if that makes sense to you others, but it makes sense to me.

Fingers crossed that it keeps on working..