[Scotty89]

My car has had this annoying suspension knocking sound since I bought it over 12 months ago and I can't figure out what it is.

It sounds like the car is driving over a boardwalk / train tracks when the ground is uneven. The car still feels firm and planted in cornering and handling, but there is a definite knocking sound over uneven roads that is very audible in the cabin.

The car came with OEM sport springs + Koni FSD (frequency selective dampening). The previous owner installed the Koni shocks, and apparently they have about 30,000km (18,000 miles) on them.

I've searched about the suspension forum and most people with similar symptoms are suggesting the sway bar links and bushes are shot.

I've since replaced both front and rear sway bar bushes and end links with the Meyle HD links. I made sure to torque them to spec, and yet I still get this annoying clunking sound.

I've had the car on jack stands to see if I can spot anything that is visually 'broken', but I can't see anything out of place. I can't see many of the bushings though as they're quite hidden under the e92.

My last thought is that maybe the frequency selective dampening valves in the Koni shocks are worn, allowing the suspension to rattle over small bumps...?

Anyone got any other ideas?

The car is now lowered on Eibach Pro springs, but the noise was present before and after - so I know it's not due to lowering the car.

[chatch10]

Is it a knocking or a rattling sound? I had more of a rattling sound and it turned out that the upper and lower shock mounts weren't tight. I had them tightened up and everything went away.

It could also be something else loose in the rear like your exhaust. Just some ideas for you to check out.

[avocet]

Can you feel it in the steering wheel? Floor? Shifter?

Engine/tranny mounts? Front subframe issues? Loose hardware(control arms etc)? Exhaust hangars?

[X_Vapor]

Originally Posted by avocet

Can you feel it in the steering wheel? Floor? Shifter?

Engine/tranny mounts? Front subframe issues? Loose hardware(control arms etc)? Exhaust hangars?

Does it have supreme power lowering perches installed by chance?

[2010MSPORT335i]

I have a similar knock on the Front Drivers side and it drives me bonkers. Im looking for anything broken or anything thats hitting eachother; I cant find anything

[pianoman224]

I am experiencing a similar issue under heavy acceleration. I'll be as detailed as possible so please bear with me!

Whenever I accelerate from 1st or 2nd gear, as soon as I let off the gas (which transfers the vehicle weight forward suddenly) there is a loud audible knock/clunk sound that I can feel under the drivers side floor under my left foot. It literally feels like someone took a rubber mallet and hit the floor underneath me very hard. It does not happen at higher speeds (my guess is because the g force change is not as sudden and violent as it is at lower speeds). The noise does NOT occur over bumps or rough road, only under the condition described above.

I didn't really have this acceleration knocking/clunk sound until after I started modding the car a year ago with Downpipes, JB4, backend flash, FMIC, Exhaust, and other mods that are very common on this platform.

After installing my downpipes a while ago, I do recall having a similar clunk when I would shift the weight of the car from side to side while turning the wheel in a slalom type manner (if that makes sense, basically at 10-20mph turning back and forth like you were trying to heat the tires up) . BUT, I figured out it was a loose steering rack (I had unbolted it for the downpipe installation). After I tightened them down sufficiently, the noise was gone.

I know that people suggest tightening the top strut nut located under the strut bar in the engine bay, but I can't seem to tighten it without it spinning on me (yes the suspension is under load). Furthermore, I would think that if it WAS loose than I would have the noise over bumps and rough roads which I do not.

Is there anything else I should be checking for suspension wise? upper/lower control arms? Should I be looking at tranny/motor mounts? Honestly, suspension is the one area of this car that I am not familiar with and I have no clue what to look for in terms of proper amount of play in bushings/what bolts to check etc.

My apologies if I , I'm just at my whits end and can't stand this noise any more! I have scoured the forums this entire week looking for an answer to this and have come up empty handed.

Relevant Car Info:

2008 E90 335i AT
FBO mods
Stock M Sport suspension

[cdgatti]

do you know the condition of the top strut mounts, they are known failure point and should have been replaced when the koni fsd were put on, but maybe they weren't

[Yozh]

Also check your guibo.

[pianoman224]

Originally Posted by Yozh

Also check your guibo.

Are you implying that "The Situation" is lurking in my car somewhere? Guess that's what I get for buying my car from the Jersey Shore.

[Scotty89]

Originally Posted by chatch10

Is it a knocking or a rattling sound? I had more of a rattling sound and it turned out that the upper and lower shock mounts weren't tight. I had them tightened up and everything went away.

It could also be something else loose in the rear like your exhaust. Just some ideas for you to check out.

I can't believe it... I went out the other night, removed the shock mounts, inspected them all and then refitted and tightened and... the sound was gone.

I also noticed that the previous owner cross threaded the bottom mount on one of the rear koni shocks but it seems to be tight enough that the rattling sound is gone anyway, and hasn't come back in the last week so I figure it's fixed.

I am relieved it was simply some loose mounts. Thanks for the tip!

[chatch10]

Originally Posted by Scotty89

I can't believe it... I went out the other night, removed the shock mounts, inspected them all and then refitted and tightened and... the sound was gone.

I also noticed that the previous owner cross threaded the bottom mount on one of the rear koni shocks but it seems to be tight enough that the rattling sound is gone anyway, and hasn't come back in the last week so I figure it's fixed.

I am relieved it was simply some loose mounts. Thanks for the tip!

Glad to hear this helped! Now get back to enjoying the car again!

[pianoman224]

Originally Posted by idk alex

I have a similar knock on the Front Drivers side and it drives me bonkers. Im looking for anything broken or anything thats hitting eachother; I cant find anything

You ever figure out what the cause of your noise was? I have new Meyle HD links coming in today so hopefully it resolves my issue, we'll see.

[spxxx]

Check the washers in the top strut mount, they need to be rounded side up facing the bearing or you'll get spring binding "thud/clunking/popping" noises.

[2010MSPORT335i]

Originally Posted by pianoman224

You ever figure out what the cause of your noise was? I have new Meyle HD links coming in today so hopefully it resolves my issue, we'll see.

Yep, took a look and my strut is blown. Would explain why it was riding like shit too.

[plmbst]

Check the strut top nut.

[pianoman224]

Originally Posted by idk alex

Yep, took a look and my strut is blown. Would explain why it was riding like shit too.

Was there an obvious visual indication that it was blown?

Installed my new end links, and while steering feels more solid it still makes the exact same noise

[pianoman224]

Originally Posted by plmbst

Check the strut top nut.

top nut is good and tight

[2010MSPORT335i]

Originally Posted by pianoman224

Was there an obvious visual indication that it was blown?

Installed my new end links, and while steering feels more solid it still makes the exact same noise

The strut was coated in oil

[Denny347]

Originally Posted by Scotty89

I can't believe it... I went out the other night, removed the shock mounts, inspected them all and then refitted and tightened and... the sound was gone.

I also noticed that the previous owner cross threaded the bottom mount on one of the rear koni shocks but it seems to be tight enough that the rattling sound is gone anyway, and hasn't come back in the last week so I figure it's fixed.

I am relieved it was simply some loose mounts. Thanks for the tip!

You actually took the strut loose from the tower? I likely need to replace my strut mounts. Was it too difficult?

[pianoman224]

Originally Posted by idk alex

The strut was coated in oil

Gotcha, mine look clean as a whistle

[e90ca]

Originally Posted by Scotty89

I can't believe it... I went out the other night, removed the shock mounts, inspected them all and then refitted and tightened and... the sound was gone.

I also noticed that the previous owner cross threaded the bottom mount on one of the rear koni shocks but it seems to be tight enough that the rattling sound is gone anyway, and hasn't come back in the last week so I figure it's fixed.

I am relieved it was simply some loose mounts. Thanks for the tip!

I believe I was having this same exact problem with my 11 335i. I only owned this car for about 5 months and it was fine up until about 2 weeks ago when I started hearing a rattle/clunk noise everytime I went over a bump in the road. It would happen on local streets and on the freeways. Took it to ST Modified in fremont and had Sean check the car out and during the test drive, he knew right away that the strut tower nut was probably loose just from hearing how the sound was happening. After tightening the nuts up, the noise is completely gone!