[leem]

I have somewhat recently noticed that there is a significant amount of rattling associated when either ABS or DSC kicks in. Beyond the normal clicking that I feel in the pedal and am used to in other vehicles, there is an almost loose part sounding rattle. I brought in to the dealer and they said noise is normal. I pressed them further and drove with a technician who agreed that the noise was excessive. After they checked it out for another day, they decided again it was in fact normal. I couldn’t find any discussion of what type of noise is normal for this system. Perhaps could someone describe how it should sound, and if it should be different than what I am used to from other cars with ABS?

[MiNiGuY]

contrary to popular belief, abs doesn't actually kick in unless you're either driving on gravel, ice or snow etc, or you hit the brake pedal as hard as you can to stop the car.
ABS - or anti brake skid - is just that. It's a CPU controlled brake monitoring system which provides independent wheel resistance control under heavy breaking or in conditions where the road surface is such that each wheel provides a different revolution reading upon normal braking.
You mention brake pedal feedback which suggests that the noise you mention is associated with braking rather than dsc so I will not go into dsc here.
By virtue of its nature, abs will be noisy when it kicks in, and although you mention previous experience with other cars I doubt that they were as small as the mini which could explain a higher noise rate. You ask how it should sound - It will sound like a lot of juddering and thumping around which in turn makes the actual feel of the car unstable and shaky, and, this can sound like the car is falling to bits in the process.
Unless you actually use your car for track racing, I find it interesting that you have time to notice the sounds the car is making under abs stop conditions. The CPU of the car monitors what is going on at all times and abs is employed if there is sharp or very heavy braking at speed. The speed could be 10mph or 110 mph but it basically responds to conditions that suggest the driver is attempting to stop immediately.
If you are simply doing this on purpose just to try it out then OK, but take into account that this is an aggressive safety feature which will not be doing your car any favours if it is consistently demanded to perform.

As for helpful advice - I would suggest that you have your brake calipers,pads and associated fixings examined on all wheels to check their condition.

All the best.

[leem]

Thanks for your reply. I suppose the car falling to bits could well describe the sound. The times I notice the ABS rattling sounds are on snow and ice, and also under any level of braking while going over a bump. Starting on snow also sometimes causes the DSC light to flash and a very similar, but shorter duration rattle. The technician explained this to me that ABS and DSC use the same hydraulic system. I am pretty sure the rattling is associated only when these two systems are activated, and doesn’t occur at all during most normal braking.

I can’t figure out how the hydraulic system could account for these noises. From my understanding it consists of basically a pump and valves and is essentially just modulating brake pressure. Although, I have no idea how it would be related to DSC.

[MiNiGuY]

Abs and dsc share the same common system.
Their basic job is to make sure that all the wheels are going around at the speeds they should be.
I'm not sure how familiar you are with either system so i'll explain very briefly what they do.
Anti brake skid and directional stability control basically monitor relative wheel speeds.
Let's say one drive wheel is spinning faster than the other or one wheel of the four is spinning in irrelevance to the other 3, the system assumes that the wheel has lost traction and applies subtle braking to that wheel in order that is can regain traction and, if relevant, subtle braking to the other 3 wheels to allow the problem wheel regain traction faster.
Because the MINI is a front 2 wheel drive car if one front wheel is braked by dsc because it is loosing traction there is a transference of torque through the differential gear to the other front wheel which is obviously the best traction wheel at that given time. This redresses the imbalance and allows the car to regain balanced traction quickly.
Abs's job is to ensure that under severe braking conditions all the wheels are providing the best braking performance, and it will act on any given wheel to stop it from skidding by reducing brake pad pressure just enough to stop the wheel skidding and then reapply pressure again hundreds of times a second in order that the car stops in the quickest possible time. This happens independently on all wheels and explains the uneasy juddering sensation as each wheel maximizes it's braking performance. It's also why the brake pedal judders because of the system override.
DSC basically does the same thing to the wheels but for different reasons. Let's say you hit a sharp bend at 60mph. The car leans heavily and the CPU, knowing your speed, instantly recognizes a difference in balance between the front and rear wheels on both sides. It implements independent wheel braking to equalize this and make the car stable through the turn. You don't feel a braking sensation because it's using the brakes to intelligently stabilize the car, not slow it down. Let's say the front or rear end of the car starts to slide. DSC instantly recognizes this and again uses intelligent braking to correct this.
Obviously both systems can only aid the driver and are incapable of correcting a situation that is out of control. It's been argued that DSC can lead drivers into believing they can drive a car better than they actually can because it's constantly correcting errors in the background.
I wouldn't totally agree with that, but it's an interesting point.

[obehave]

It could simply be air in the brake lines as well. If that gets trapped in the reservoir pump it'll make a hash out of the pressures as it tries to function. Cold weather doesn't help.
Just a thought.