Need help diagnosing a "clunk" when braking quickly

[pgolimowski]

ok So I did some extensive testing last night and here is what I found.
1. Noise is the same with transmission in D or N - probably not tranny related
2. makes no diffidence if I come off the gas fast or slow or not at all - probably not brake assist but not ruled out

Another thing I noticed is if I stab the brakes there is a tiny lag and then they grab with the clunk sound and what seems like overly aggressive braking. If I am already on the brakes and I stab hard it brakes normally with no noise.
These last part has me thinking it might be pad related. Maybe a pad is lose but once it makes contact with the rotor slowly it acts normally...thoughts?

[petro55]

Hello, I have the same problem did you ever resolve this issue?

[pgolimowski]

Not yet. I have replaced the front pads and rotors as well as bled the brakes with no change. If you have better luck I'd love to hear about it.

[kkodal78]

I had the samething on my 4.6 and it was cured after replacing the control arms.

[watrob]

Do you have adaptive drive?

If so the chance is play in the front electonic/ hydraulic swaybar, you cannot tell while the X5 is standing still as the swaybar is under tension, it has to be loosen off so you can twist it manually to see if the hydraulic mechanism or valves have play in them.

It was a well known problem in the early models and a revised new front AD swaybar was made available.

[crazyj23]

Sounds like motor and/or transmission mounts

[petro55]

I dont have adaptive drive. My noise started as a loud clunk if i would touch the brakes, now has turned into a clunk followed by a brake squeel. I am going to take the left side breaks off tomarrow and check them out. They have plenty of meet on them, so maybe a retaining spring or something on the caliper is loose. I will post the results.

[petro55]

Fixed my problem! My brake caliper was sticky. I removed the bolts that hold the caliper and lubed them up with antiseize. No more clunking or squeeking. I cant believe i lived with this noise for the last 6 months and thats all it was. I accidently broke the brake sensor opps... I have about 6 more months of pad life left.

[grey]

Originally Posted by pgolimowski

I have an 08 x5 4.8 with about 45k miles. Only have had this car for a few months so I'm not sure how long this has been going on. When I push the brakes slowly, it brakes normally. If I push them quickly, but not necessarily hard, it makes a loud clunking noise that can be heard and felt in the pedal. Before my warranty ran out I had dropped it off for service and had them check the brakes and they said they were normal. This is about my 10th BMW and this can't be normal. Any ideas of what to check would be appreciated.
Thanks
Patrick

Have u fixed it yet?
Get the front thruster arms Inspected by a suspension mechanic. You drve slowly and hit the break, hear a loud noise. Thruster arms fail very commonly on the e70' and even on the e71s my mechanic said. They're not that expensive.