Cold start rattle/noise

Just bought a 2012 X3 3.5i. On cold start there is a engine or exhaust rattle. I picked the unit up at the PC and heard it. I was told the 3.5i's have this sound until the catalytic converter heats up. The sound does go away shortly after start-up. Anyone else hear this with their X3?

to me mine sounds just like the starter doesn't disengage.

I've heard this on various BMWs with the turbo I-6, so I wouldn't worry about it as long as it goes away.

Yeah, my wife was pulling into the garage the other night and I heard a rattle. I climbed underneath and it looks like it is a loose cat shield. Will note it when it goes in for service next.

Finally took the X3 in to have them listen to the noise at cold start. They listened to another 3.5 and determined it was the same. They stated is was likely a rattle coming from the turbo's pressurizing.

Not buying this & looking to see if anyone else has had this issue. The metallic rattle only happens on the first 10 seconds of a cold start when the fast idle slows to normal operating speed. The noise is horrific in my opinion as it sounds like something one would expect from a poorly designed vehicle.

Any input would be appreciated.

FYI, had a 2nd opinion on the issue. We both crawled under the vehicle several times to pin point the sound. It appears to be an noise coming from the wastegaate on the turbo. Those who may have a similar rattle sound you may want to suggest to the dealer to look at the wastegate.

Must be separate rattles- no wastegate on the 28i.

Sometimes I have to smile at how everything is scrutinized to the last detail on this forum. You have asked a good question......is this noise a problem or not. My experience with my 2012 X3 is the same. Noise disappears after 10 seconds on a cold start. Sounds like a really rough idle, but then quickly smoothes out. I'm not worrying about it. Car runs fine.....I have had not a single problem. I assume that there is nothing wrong with this vehicle and have put it behind me. I don't think it's not a build quality issue. Or to put it another way, I'm not sweating the small stuff.

We were told by the dealership (sales guy) that the cold start rattle heard on our 2012 X5 Sport is the "turbo starting up". In my opinion, this is a horrendous noise that should not be heard on a vehicle in this price point. I am taking the truck in today to have the tech take a look. It does seem to go away after 10 or less seconds, and the vehicle drives fine. Nonetheless, it is a horrendous noise.

Originally Posted by drbmw

Sometimes I have to smile at how everything is scrutinized to the last detail on this forum.

Yep. And it's the "price point" stuff that really kills me.

Anyway, it's a machine - machines make noises.

So I'm curious as to why the "price point" comment would "kill you"? After spending this kind of money on this particular machine (my 7th BMW) I was not expecting it to sound like the car my 16 year old neighbor drives. Clearly, I am not the only person to have experienced this sound nor to be bothered by it. My apologies if my comment bothered some of you.

Originally Posted by sabreu

My apologies if my comment bothered some of you.

No apology necessary. You are allowed to feel entitled - I just think it's silly.

Any updates on this? My 2/12 production 35i makes the same sound on cold startups.

No updates. Have service appointment next week. Will keep you posted!

Mine does it too. I noticed this too when I took test drives so I'm not too concerned, especially if a lot of people have been mentioning this. I'm under warranty, car is running great, and the noise goes away after 10 seconds or so. But I do agree that the noise is a little disconcerting at first.

Originally Posted by sabreu

No updates. Have service appointment next week. Will keep you posted!

I agree with you sabreu
Luxury vehicles should not sound like cheap rattling crap for any period of time. 10 seconds or ten minutes it is still annoying
I am sure german engineers could solve this noise issue.

My wife's 28i rattles at idle--hot and cold. It's annoying and really makes the vehicle sound cheap/poorly built. The shop recognized the noise, said they checked out another 28i off the lot and it had the same rattle. According to them it must be normal. If it is, it shouldn't be. I sweat the small stuff and bought BMW because I thought they did too.

Agree. I heard it again the other day while the car was idling in the driveway. I just do not have the patience to deal with the bull**** excuses (like the one you got).

I heard the same noise when I first started my 2011 X 3.
3.5I.
Brought it to BMW service center to have it checked out and was told that the noise is due to the twin scroll turbo on this engine. The noise subsides after about ten seconds and the car runs smoothly without any issues, however, I do admit it can be irritating when you first hear it. I see that this seems to a common problem with the X3 in line six twin turbo engines.

Don't forget you are basically driving a diesel (that burns gasoline). In fact BMW is the first car company to offer only turbo (lagged), direct injection (rattly), bottom heavy (HP <= TQ) to the US.

So it shouldn't surprise you that there is rattle at startup. Notice also that most of the F25 engine noise you hear in from the induction side, not the exhaust side. This increases one's perception of valve noise. This may be exacerbated when the engine is cold due to some emissions component.

..and has an ignition system with spark plugs..and a compression ratio 1/3 of a diesel engine...
Our 2.8 is not turbocharged and has the same rattle.
Back to the Kool Aid pitcher....

..and has an ignition system with spark plugs..and a compression ratio 1/3 of a diesel engine...
Our 2.8 is not turbocharged and has the same rattle.
Back to the Kool Aid pitcher....

Anyone have any luck with resolution to the start-up noise? The issue I have has continued and seems to last longer now that the vehicle has more miles. I was hoping to hear of a tech bulletin before wasting time to have them look at it again only to tell me again it's not unusual.

Experienced the same noise(rattle) when I first started my 2011 X3 3.5I X drive. Was told that this was normal with the twin turbo at initial start up. Noise does go away after 10 seconds or so. Vehicle runs fine otherwise.My only complaint so far is the throttle lag after stopping at a light. Will address this with BMW when I go for my first service at 15000 miles.

Hmm, my car has the start up rattle too. The noise is typically gone before I shift the car into reverse so I'm not sweating it. I will however watch this thread for any concerning developments.