[stevenkh]

My 330i is a manual shift. When shifting from 1st to 2nd at a low rpm and putting the car under a little of a load, I'm getting a loud rattle coming from under the car in the rear. Once I get the rpm's up it smoothes out and goes away. It sounds like an exhaust rattle or one of the plastic under shields.

Has anyone else experienced this? It is very intermittent but annoying.

[jayely1]

emm don't shift at such a low RPM.. What RPM are you shifting at when it occurs?

[stevenkh]

Approximately 2500 to 3000 (normal). Actually sometimes it does it at higher rpm's as well.

[jayely1]

Like a rattle in the trunk or a mechanical? Still have a warranty?

[stevenkh]

It is a metallic type sound. I think it is a exhaust rattle. I have been looking here on the forums for the past 2 hours. I have it narrowed down to either an exhaust bracket or clutch rattle.

I have 5,000 miles left on the warranty. I guess I will just take it in to the dealer.

[jayely1]

yeah, it hard to say not being able to here it. take her to the stealership.

[Fresh330]

WOW... just noticed this on my '06 330xi. Like you, I pin pointed it to my rear wheels when I'm in 1st/2nd gear. You can hear it when you let off the gas, it's a metallic rattle. I think it's the brake shield rattling but now that you mention it, maybe exhaust. Btw, I drive an auto.

Stevenkh, I have an appt this Thursday the 13th. I'll let you know how it goes.

[reegs]

I have the same sound on my manual 2006 330i. I've been really worried about it. It even rattles when I start it up and its cold. If it's warm, it doesn't rattle though when I start it. I get it between 1st and 2nd gear and when I left off the gas and let the engine slow the car down.

...following this thread...

[lonestar22]

ive had this problem since i got my car like a week ago. but mine is in the front, in the someone right behind the front wheels underneath the car. u can hear it after i drive for a few minutes while the car is idling. makes my car sound like a POS. im taking it to the dealer this week sometime to see if they can find it. its hard to replicate once your at the dealer but it happens all the time when im out and about, especially in front of people.

i also get a rattle while the engine is shutting down. seems to be coming from the transmission.

subscribed for more info

[augustxii]

dang the op guessed right, i've been having the same rattle and just a few weeks ago i took it in. let the SA drove the car with me and found out that the exhaust bracket was broken. cost 170 bucks to fix since i didn't have the coverage

[samchoi604]

I'm guessing you got the car used? From my experience, cars that have been sitting outside on the dealer lot often get this problem.. or cars that are parked outside by the owner. Something underneath has rusted (most likely the heat shield) and it's causing that rattling.

At certain RPM, a frequency of vibration coming out from the exhaust or engine is able to resonate to the rattling part. The rattling part might not respond to other frequencies. That is why it only happens only at certain RPM's.

[TommyK]

i dont have that, sorry, if you take your car to the dealer GL with getting them to do anything, every time i tell them to check the brakes when they squeak they tell me they cant replicate it and skip out, and then i pick it up and squeaks like a bitch when i reverse.

my brakes make a click sound in the rear when i apply my foot to the brake. but that is andi have 35k miles

[Fresh330]

dang the op guessed right, i've been having the same rattle and just a few weeks ago i took it in. let the SA drove the car with me and found out that the exhaust bracket was broken. cost 170 bucks to fix since i didn't have the coverage

No coverage? Are you out of warranty on your '06?

Subscribed as well, although I have an appt this Thursday w/ the dealer.

[BK]

I'll state the obvious, since we see this happen all the time here -- check the vents under the front seats to make sure no loose change has fallen in there to rattle around.

Doesn't sound like that's your issue, but someone with that issue will inevitably find this thread using the search tool and I'll be a big hero.

[Mendossa]

Originally Posted by stevenkh

My 330i is a manual shift. When shifting from 1st to 2nd at a low rpm and putting the car under a little of a load, I'm getting a loud rattle coming from under the car in the rear. Once I get the rpm's up it smoothes out and goes away. It sounds like an exhaust rattle or one of the plastic under shields.

Has anyone else experienced this? It is very intermittent but annoying.

^^^^ THIS. I had the exact same thing, brought it in, the dealer said it was "normal brake noise"...

In the end, it was the butterfly valve inside the right tail pipe of my exhaust. If you look carefull, there is a metal part that flips (closes) inside when:

A) car is cold OR
B) under 3000rpm OR
C) in "lean" mode, like when you are cruising around at a stable speed

In my case, the valve was rattling when closed, I guess exhaust pressure was making it flick semi-on/off causing the noise. To make sure my diagnosis was right, I zip-tied the rubber vaccum line that activates the valve (search "golf tee mod") to turn it completely off. In this state, the valve is always open.

The rattle completely disappeared. You might want to try this to see if you have the same issue.

[GregL]

Originally Posted by Mendossa

^^^^ THIS. I had the exact same thing, brought it in, the dealer said it was "normal brake noise"...

In the end, it was the butterfly valve inside the right tail pipe of my exhaust. If you look carefull, there is a metal part that flips (closes) inside when:

A) car is cold OR
B) under 3000rpm OR
C) in "lean" mode, like when you are cruising around at a stable speed

In my case, the valve was rattling when closed, I guess exhaust pressure was making it flick semi-on/off causing the noise. To make sure my diagnosis was right, I zip-tied the rubber vaccum line that activates the valve (search "golf tee mod") to turn it completely off. In this state, the valve is always open.

The rattle completely disappeared. You might want to try this to see if you have the same issue.

Interesting. I'm convinced my exhaust valve squeaks when it opens so it may be related to my underbody rattle too. For example when I'm at a complete stop, then turn through an intersection and accelerate to 80-90km/h I clearly hear a momentary "bwoot" sound from the rear, like...uh... like a metallic flatulence.

Did you hear your rattle with the windows closed, or only open? I only hear mine when I have a window down and at parking lot speeds.

[Mendossa]

Originally Posted by GregL

Did you hear your rattle with the windows closed, or only open? I only hear mine when I have a window down and at parking lot speeds.

Only with windows opened at parking lot speeds. When I took it to the dealer, I actually specified "drive it slowly around an interior parking lot with the windows down, you can't miss it". In my case, it was getting worse as time went by.

I live in a narrow one-way street with cars parked on both side and everytime I would turn into my street (windows down) and engage 2nd gear I'd hear some kind of a soft clunk and then this damn rattling noise bouncing off the parked cars.

[GregL]

Originally Posted by Mendossa

Only with windows opened at parking lot speeds. When I took it to the dealer, I actually specified "drive it slowly around an interior parking lot with the windows down, you can't miss it". In my case, it was getting worse as time went by.

I live in a narrow one-way street with cars parked on both side and everytime I would turn into my street (windows down) and engage 2nd gear I'd hear some kind of a soft clunk and then this damn rattling noise bouncing off the parked cars.

Thank you very much, I'll bring this up when my car goes in for service later this month

[K330i]

low RPM / idle exhaust rattle:

the exhaust bracket directly behind the engine. found it to be loose but could NOT get the dealer to fix it. investigated it myself and realized the bracket would not tighten it enough to get rid of the noise. so stuffed some exhaust wrap in between the bracket and the pipes and tightened it back down.

been 3 months and no rattle......

[lonestar22]

trying this tomorrow, can i just shake the exhaust and replicate the noise manually when the car is on a lift?

[K330i]

Originally Posted by lonestar22

trying this tomorrow, can i just shake the exhaust and replicate the noise manually when the car is on a lift?

probably...but you can just reach up there and shake the bracket and you'll know if it's the culprit.

if it is, just back the bolt out, stuff some heat wrap in there and tighten it back down. i actually cut my wrap to cover as much of the clamp that was touching (both) exhaust pipes. i can try to post up some pics if you want.

[**Matt**]

This thread couldn't have better timing. I bought my CPO back in May and lately with the windows down I hear this same noise when coasting into my driveway, still in gear, just not accelerating. This noise goes away as soon as I press in the clutch. I'm worried that it's something with the trans, but hoping it's only the exhaust bracket. Will check it out tonight.