[KGB_123_99]

Hi folks,

I recently noticed a start up rattle on my 2013 328iX that only happens when the car is cold (and it's not the N20's injector noise ). It is there at idle and becomes more obvious if I blip the throttle. The noise goes away after about 2-3 minutes once the exhaust warms up.

I took the car to the dealer who said that some rattle on warm up is normal and within BMW spec (really?). This morning I decided to tap various parts of the exhaust to see if I can reproduce a noise. Here is a clip of one area which doesn't sound right. It is the best shot I could get without raising the car.

What do you think? Is this sound normal? My car has just over 3000 miles on it.


Thank you for your input!

[KGB_123_99]

Here is another video with the engine running. Maybe a bit more helpful...

[KGB_123_99]

No opinion, anyone?

[Austinformedude]

I have this EXACT same problem on my 2013 328. It has been there for a while. I am taking it to the dealer to fix next week, so will let you know. I am pretty sure there is something broken inside the muffler, as I can't find anything loose and banging on it revealed nothing.

[KGB_123_99]

Thanks a lot, I will appreciate it if you can let me know what the dealer tells you. I'm starting to think that it's the exhaust valve in the muffler that resonates.

[Austinformedude]

Originally Posted by KGB_123_99

Thanks a lot, I will appreciate it if you can let me know what the dealer tells you. I'm starting to think that it's the exhaust valve in the muffler that resonates.

We just got the car back from the dealer. They had it for two days and said were "unable to duplicate the rattle" I showed the CA and the tech the rattle when I dropped it off and they both agreed it was an issue. When I picked it up, the rattle was gone, despite being there for months. Honestly, I think they did something but aren't telling (like perhaps rev the car up really high to blow out whatever was in there?!?!) If it comes back, I am driving right back to the dealer.

[Falafel Combo]

Same rattle here on cold starts only. 2013 335i M Sport.

[Halsifer]

Originally Posted by alpinweiss 335i

Same rattle here on cold starts only. 2013 335i M Sport.

I believe that's the exhaust flap rattling is what you might be hearing. Mine rattles on cold start as well. But after two minutes, you'll hear the flap open up and the rattle disappears.

Not too sure whether or not the 328i has a flap, I doubt it does though...

[Austinformedude]

Yeah the 328i has the flap. This noise is def NOT that flap, although the flap can rattle sometimes. When the noise occurs, one can manually open and close the flap and there is no change to the popcorn sounding noise. It almost sounds like a heat shield rattle, but much louder.

[KGB_123_99]

Originally Posted by Austinformedude

Yeah the 328i has the flap. This noise is def NOT that flap, although the flap can rattle sometimes. When the noise occurs, one can manually open and close the flap and there is no change to the popcorn sounding noise. It almost sounds like a heat shield rattle, but much louder.

Thank you for the update. I stopped by the dealer this week for this problem again, only to get the "It's normal!" answer. The dealer started five 328s (2014) while I was there and 4 out of 5 had this rattle. Their theory is that it's the exhaust flap and nothing can be done about it unless it becomes bad enough and then they will replace the entire muffler.

Also, I'm starting to hear some buzz/rattle under moderate throttle between the shifts that seems to be the flap briefly rattling when it opens/closes. I will try disconnecting the flap altogether to see if that solves the problem.

[fredsf30]

I also have this EXACT problem on my car!

Cold starts is when it happens, and it sounds something like an exhaust shield rattle.

I am quite sure it's not a big deal, but that's not how a new BMW should sound on start.

It sounds like a 1989 civic with an exhaust leak.

I will update everyone when I bring it in next week. I will tell them that if they can't fix it, they must put on the performance exhaust!!! LOL

[Austinformedude]

Fixed! Finally convinced the dealer to replace the muffler assembly under warranty. This completely fixed the problem! It appears that sometimes the baffles inside the muffler become detached and rattle inside when warm (bad welds?) So if your problem is not with the flap, or heat shields, the next step would be replacing the muffler.

[ASV731]

I had a similar rattle but assumed it was the exhaust flap on my 328. When I disconnected the actuator and used exhaust wire to keep the flap open at all times the rattle went away.

[Fronzdan]

Well I have this now. Same symptoms - it rattles at start, clearly metal on metal and goes away quickly once warmed up. Without looking and before I read this thread, I thought "heat shield". I guess I'll bring her in...2014 335.

[KGB_123_99]

Dealer couldn't find any loose heatshields or anything else in the exhaust. Apparently it is the wastegate rattling a bit when cold and is considered normal.

[Fronzdan]

Now all we need is for people to start thinking this is super cool, like burbles and we'll be bad ass. Then guys will be dumping steel ball bearings into their muffler to get that rad metallic buzzing sound.

[t335xi]

I get a vibrating rattle also, but its more during shift points

[spindzz]

sorry to bring up old thread...

This just started to happen to my car and of course i'm out of original warranty, but I do have CPO warranty. Not sure it'll cover it.

Is this the same as what everyone's talking about?

Anyone have a clue what this is:

[KGB_123_99]

That's the exhaust flap on a cold start. My dealer refused to fix this saying it's normal.

It goes away in a minute or so.

[Alpine435]

I had a really bad rattle as well, it turned out to be my exhaust flap. It seemed like the linkage between the actuator and the flap broke off. So even after the cold start was over it still rattled like crazy. So Instead of going to the dealer for a warranty fix because I'm FBO so they might give me crap for it so the solution I came up with was to just weld the flap in the open position lol!! Only took 2 minutes and I was all done.

[motorwerkeman]

I had a rattle that sounded like exhaust as well, only when warm blipping the throttle off idle, and over certain bumpy parking lot surfaces. 2012 N20 car with 23,000 miles.

Turns out the dealer found the something inside the catalytic converter loose causing the rattle after 2 says of investigating. BMW has 8 years emissions warranty so the SA has told me a new one will be covered free of charge.

[DJsirkit]

My Car i hear a ticking sound even after driving it for awhile and the car is warmed up. The sound is similar to when you shut-off the car and hear the car cooling down almost like a ticking. I hear this while the car is at idle. Could this be just because its cold out?