Clunk/thumb noise during braking or low speed garage turns (under 5 mph)

[DetroitP]

Hi Everyone & Thanks in advance for your time,
I have a clunk sound that I can't seem to figure out what's causing it. Let me start by describing the vehicle:

Vehicle:
2008 E92 M3 DCT, supercharged, and everything else is stock (EDC dampeners).

What I have done or checked:
1) Replaced engine mounts, sway bar bushings, and end links.
2) During the engine mounts replacement (did them myself), I did replace the tie-end steering rods (alignment done also) because they were fairly rusty and I couldn't get them off.

The issue seems to be prominent when I do a drive to reverse or reverse to drive maneuver while applying the brakes. To me it seems like whenever the suspension travels and settles, followed by applying the brake the thumb or clunk sounds appears.

I suspect the struts may be at fault, especially front driver side but I am not sure how to check if it is the cause before I make a replacement purchase. Anyone else has had a similar issue or knows what I should check next?

Thanks

Update: 9/4/2021 Issue Resolved
Changed the front brake pads and the issue is resolved. The previous pads had plenty of life on them so I am not certain of the correlation but it is resolved now. If someone has a good explanation it would be helpful to know. Thanks

[ganz]

It could be driveshaft u-joint. Do a forum search on that term and many videos of the issue are there to confirm if it is the same sound.

[bbnks2]

sounds like brakes... check the caliper guide pins are tight... if using aftermarket pads they may knock in the caliper as well due to less tight of a fitment.

[Hivand_M]

Originally Posted by DetroitP

Hi Everyone & Thanks in advance for your time,
I have a clunk sound that I can't seem to figure out what's causing it. Let me start by describing the vehicle:

Vehicle:
2008 E92 M3 DCT, supercharged, and everything else is stock (EDC dampeners).

What I have done or checked:
1) Replaced engine mounts, sway bar bushings, and end links.
2) During the engine mounts replacement (did them myself), I did replace the tie-end steering rods (alignment done also) because they were fairly rusty and I couldn't get them off.

The issue seems to be prominent when I do a drive to reverse or reverse to drive maneuver while applying the brakes. To me it seems like whenever the suspension travels and settles, followed by applying the brake the thumb or clunk sounds appears.

I suspect the struts may be at fault, especially front driver side but I am not sure how to check if it is the cause before I make a replacement purchase. Anyone else has had a similar issue or knows what I should check next?

Thanks

I just got my car (2011 e92 dct) and noticed this as well. I only notice it in my work's parking structure when as I brake, turn, shift to reverse to back up into my space. I too notice it coming from the drivers side.

Curious to know what the issue/solution is.

[bbnks2]

Originally Posted by Hivand_M

I just got my car (2011 e92 dct) and noticed this as well. I only notice it in my work's parking structure when as I brake, turn, shift to reverse to back up into my space. I too notice it coming from the drivers side.

Curious to know what the issue/solution is.

could be strut top mounts

[DetroitP]

Originally Posted by bbnks2

sounds like brakes... check the caliper guide pins are tight... if using aftermarket pads they may knock in the caliper as well due to less tight of a fitment.

That is very interesting... never thought of that and I will check them. Thx

Originally Posted by bbnks2

could be strut top mounts

I inspected them and everything seemed to look "healthy". Are you referring to the rubber that lays over the top hat?

[DetroitP]

As far as the brake inspection, are you referring to the star bolts covered by the grommet in the attached pic?
I just tightened them and the noise seems to have disappeared... I will sped a couple of more days driving to confirm and will let you guys know if it had made a difference.

Thanks again for ur help

[bbnks2]

Originally Posted by DetroitP

As far as the brake inspection, are you referring to the star bolts covered by the grommet in the attached pic?
I just tightened them and the noise seems to have disappeared... I will sped a couple of more days driving to confirm and will let you guys know if it had made a difference.

Thanks again for ur help

yes those pins seem to back out on me often. I use blue Loctite on mine now because I am afraid I might end up over-torqueing them trying to prevent them from loosening up. When they get a little lose you get a nice pops from the brakes.

And yes, I was referring to the rubber top hat. They collapse.

Could be many other issues but those two are common things to cause knocking noises.

[DetroitP]

Thanks! I did the driver side and it didn't help. I am going to try the passenger side next and see how it goes.

[atopa2002]

Originally Posted by DetroitP

Thanks! I did the driver side and it didn't help. I am going to try the passenger side next and see how it goes.

Do you still have your oem splash panel ?
The metal hangers can make a similar sound when going over bumps at low speed or apply the brakes.
Especially when the 2 side pieces are not attached the hanger are not as tight .

Tapping on it to check if it makes a similar sound.

[DetroitP]

Originally Posted by atopa2002

Do you still have your oem splash panel ?
The metal hangers can make a similar sound when going over bumps at low speed or apply the brakes.
Especially when the 2 side pieces are not attached the hanger are not as tight .

Tapping on it to check if it makes a similar sound.

Yes, I have all the splash panels intact and secure. Thanks for the suggestion.

[gmx]

Originally Posted by bbnks2

yes those pins seem to back out on me often. I use blue Loctite on mine now because I am afraid I might end up over-torqueing them trying to prevent them from loosening up. When they get a little lose you get a nice pops from the brakes.
.

Hmm, good post. I replaced rear rotors and the noise coincidently went away. Probably because I torqued the guide pins to spec this time after completely cleaning them, the caliper, and hub. I'll keep an eye and ear out, nice tip.

[DetroitP]

Originally Posted by bbnks2

yes those pins seem to back out on me often. I use blue Loctite on mine now because I am afraid I might end up over-torqueing them trying to prevent them from loosening up. When they get a little lose you get a nice pops from the brakes.

And yes, I was referring to the rubber top hat. They collapse.

Could be many other issues but those two are common things to cause knocking noises.

You were right!
Changed the front brake pads and the issue is resolved. The previous pads had plenty of life on them and the two screws and on tight so I am not certain of the correlation but it is resolved now. Thanks

[Wally1552]

I'm glad you found the issue but it sucks spending money and parts just to have it not fix it. My local shop charges about $100 to diagnosis issues including scanning with ISTA and then I fix it myself. It saves money in the long run for me.

[BMotorenWerke]

DetroitP - Thanks for the update on this

I also have a similar problem, expect I don't hear the clunk on reverse gear but only in very low speeds in first and not every time either. Everything is stock on the car - 2012 e92

Local BMW indi tech shop couldn't diagnose, it doesn't happen every time.
I tried taking some pics of the sway bar end links

Any feedback on how these look? I realize it might be hard to say for sure, but I thought I'd start here before checking more (Im swapping brake pads soon for other reasons)

[DetroitP]

If you can "wiggle" the sway bar end links, and don't hear any clunks, then I would defiantly check the two screws on the calipers (behind the rubber grommet) and ensure they are secured. The screws on the calipers were my issue, and I plan on replacing them soon to avoid future issues.

[bbnks2]

The pads them-self can be the source of a clunk... especially if you can reproduce the clunk by applying the brakes rolling forward... then put the car in reverse and if you get a pop as soon as you tap the brake in reverse it's likely to be a caliper/pad problem. Sometimes the aftermarket pads fit loosely in the caliper and knock when they resettle each time you tap the brakes. Sometimes pads don't come with backing plates and people dont transfer the stock ones over... the pad now take sup less room in the caliper... clunk.

[DetroitP]

Update:
after replacing the older pads with new ones, and accumulating approximately 2000 miles, the clunk is starting to appear again.
I called manufacturer/retailer of the pads, and they said it was normal. Obviously that was the short answer they could come up with.

Any suggestions on what I should try next?
Thanks