[Kaneda215]

Update: They applied some sort of silicone insulation to the C-pillar frame and the noise is no longer happening. They opened up a PUMA case for it as well. Unfortunately, they put a small dent in the car while troubleshooting, but were able to get the dent pulled to 98% (so it's not noticeable unless you're really looking). I ended up contacting BMWNA about the incident. That coupled with having to take a new (CPO) car in so many times within the first 2 months of owning left a very bad taste in my mouth. They ended up extending my CPO warranty from 5 to 6 years in compensation. Ultimately I'm very pleased with BMW and how they handled my situation. PM if you have any questions.



I've got a 2017 BMW 330i CPO (10k miles), that has developed a very strange and annoying sound when driving off from a standstill. I've already taken it to BMW so that they could spend a few days "troubleshooting" the issue... eventually ensuring me that they had fixed it. Of course, within 30 seconds of driving off I heard the sound again.

Description: A single knock/clunk that is pretty audible with no music playing. It sounds like it's coming from the rear-left and it happens only when driving off from a standstill. This sound doesn't happen 100% of the time either. I can probably replicate it 40% of the time under certain conditions.

Possible origin: I only started to notice this sound after putting the rear seats down for the first time.

Possible causes and attempted fixes:
1. Nothing in the trunk is moving around.
2. BMW removed the rear seat and drove around with the sound still present.
3. They removed all of the rear panels and torqued all bolts to spec with the sound still present.
4. They removed some of the panels in the trunk and said that a bar (I forget the technical designation) across the amplifier was loose. They applied some foam and tightened it down, stating that this fixed the problem.

It wasn't fixed.

Further troubleshooting:
1. I feel like there isn't anything rolling around in some panel. It ONLY happens after the car accelerates from a full stop, and possibly very faintly when coming to the stop.
2. Apparently it isn't the seats. BMW removed the rear bench entirely and drove around with the noise still present.
3. Could it be suspension related? I find it strange that it doesn't happen while driving (unless I can't hear it)... and only happens after coming to a full stop.

The car is very smooth on the road and beside this isolated noise, the cabin is relatively quiet. I'm hoping someone out there can help me diagnose the problem or better yet, has a solution.

[RoundelM3]

Have them check the brake pads/calipers. Might be pads moving slightly or a loose caliper. Could also be a shock absorber or other suspension component.

[sspade]

Im pretty sure I hear this same noise every morning as I back out of my garage, driveway and then take off.

[Kaneda215]

Originally Posted by roundel335

Have them check the brake pads/calipers. Might be pads moving slightly or a loose caliper. Could also be a shock absorber or other suspension component.

It definitely shouldn't be the rear brakes. They actually fixed a different issue by replacing the rear rotors, pads, and sensors.

I don't hear the noise going over any sort of bumps, or even while driving AFTER the initial drive off from a standstill. It only happens after coming to a full stop and doesn't even happen most of the time.

[Kaneda215]

Originally Posted by sspade

Im pretty sure I hear this same noise every morning as I back out of my garage, driveway and then take off.

A pretty noticeable pop that sounds like it's coming from the interior rear-left? Do you usually have the radio playing the rest of your commute, therefore not hearing it during following stop/drive-offs?

[tex2670]

Ask if you can have a tech ride along with you so you can point it out to them when it's happening.

[Kaneda215]

Originally Posted by tex2670

Ask if you can have a tech ride along with you so you can point it out to them when it's happening.

Good recommendation, but I already did that on my last trip to BMW, and they were unable to fix it properly. Before I resort to taking it back and risk losing the car for another week, I'd like to see if anyone else has had a similar problem and discovered a fix.

[rak299]

My guess is rear shock.

[BMWtight2me]

I heard a sound like this. Same thing, a clunk noize front the back left. Launched the car one day, snapped the rear axel in two.

[bimmer456]

Could be the engine mounts

[Beek]

Unlikely this is it, especially since you suspect noise is left rear but could the battery be loose? Easy to check anyway, good luck!

[lkstaack]

I'd guess drive shaft.

[Kaneda215]

Originally Posted by Beek

Unlikely this is it, especially since you suspect noise is left rear but could the battery be loose? Easy to check anyway, good luck!

Haha I wish... just checked and it was really secured in there.

Originally Posted by rak299

My guess is rear shock.

Wouldn't there be a repeat sound while driving around? I don't think it makes sense that you ONLY hear this single knock while accelerating from a full stop.

Originally Posted by lkstaack

I'd guess drive shaft.

Same as previous reply to the rear shock.



I just got home and sat in the back seat while driving it around. It actually doesn't sound like it's coming from inside the cabin, but perhaps the C column? I guess something suspension related in the rear left as well?

[chiefneil]

Does it happen any more or less frequently depending on how hard you stop? Could be something like a bad bushing or loose coupling somewhere in the suspension that's shifting around. Try a few hard stops and semi-quick starts to see if that makes it more reproducible for a tech to hear.

Also try with the windows down on the off chance it's related to the window mechanism.

[beecee]

I think its the exhaust valve flap opening. Does it sound like this -

[sspade]

My car definitely has this same issue. Mine makes a slight clunk/tick every movement forward from a stop. Sounds like its coming from right rear suspension on my car. Super annoying. Last thing I want to do is waste time at the dealer trying to diagnose a mysterious noise.

OP please keep us posted on what your issue is or is not related to...

Im due for service in about 3k miles and want to wait until then to have them look at it. Should be right around the 1st of the year.

[Kaneda215]

Originally Posted by chiefneil

Does it happen any more or less frequently depending on how hard you stop? Could be something like a bad bushing or loose coupling somewhere in the suspension that's shifting around. Try a few hard stops and semi-quick starts to see if that makes it more reproducible for a tech to hear.

Also try with the windows down on the off chance it's related to the window mechanism.

Good tips. I tried to see if having the window down would stop the noise. Unfortunately it still happened which leads me to think that it has nothing to do with the window mechanism.

I can replicate it almost every time when stopping hard in reverse, then moving forward in drive. Also, it was much easier to replicate it this morning when it was cooler out. As the San Antonio temperature rose throughout the afternoon, it was much harder to replicate the noise. So, it seems like this may be temperature related.

Originally Posted by beecee

I think its the exhaust valve flap opening. Does it sound like this -

It's definitely not that. That car sounds great though.

Originally Posted by sspade

My car definitely has this same issue. Mine makes a slight clunk/tick every movement forward from a stop. Sounds like its coming from right rear suspension on my car. Super annoying. Last thing I want to do is waste time at the dealer trying to diagnose a mysterious noise.

OP please keep us posted on what your issue is or is not related to...

Im due for service in about 3k miles and want to wait until then to have them look at it. Should be right around the 1st of the year.

Will do... I'm definitely hoping to pinpoint the issue BEFORE taking it back to the dealership.

[Kaneda215]

I got around to having some videos taken on two separate occasions. The sounds heard while stopping/accelerating are almost identical to what I hear inside the cabin.

[dsc888]

Originally Posted by roundel335

Have them check the brake pads/calipers. Might be pads moving slightly or a loose caliper. Could also be a shock absorber or other suspension component.

I will 2nd the idea of it being brakes. It's a known issue on some cars where the brake pads shifts slightly in the bracket and causes a SINGLE pop noise. I used to own a 1997 Toyota Camry V6 that did this with OEM pads when I went from D to R while backing out of a parking space. It was 100% reproducible.

[beecee]

Originally Posted by Kaneda215

I got around to having some videos taken on two separate occasions. The sounds heard while stopping/accelerating are almost identical to what I hear inside the cabin.

This does sound like the exhaust valve flap opening. It's weird because I went to bmw for this same "problem" and they couldn't seem to diagnose the problem but then I looked on YouTube and found what it was.

[Kaneda215]

Well I just got back from the dealership after a quick troubleshooting session. The noise in my video is apparently coming from the caliper slide pins... which according to the technician is normal.

They took the car in for about two hours and checked for shifting pads or any worn suspension components (bushings, etc.). Everything looked good and without leaving the car there for a few days, we couldn't figure it out. The foreman suggested that the cause is due to some sort of torquing, as the sound apparently only happens while turning around uneven surfaces.

I guess I'll see if it just fixes itself over the next few months as the car breaks in a little more. The foreman assured me that everything is in perfect working condition and that I should enjoy the car.

[sspade]