[aerostar]

In true BMW fashion, I have a problem at 30k miles.

[USA-RET]

Geez, that sounds awful. Warranty Time!

[mike@x-ph.com]

Sorry about that OP

[BMWZ4]

Yep, warranty time! Might also be a loose bolt too...I wouldn't be too worried.

[Dylan86]

Loose exhaust flap/valve? They go south pretty often too.

Not the worst (first) issue to have

[stylinexpat]

My sister's does the same thing. Happens in the morning when car is cold

[aerostar]

Originally Posted by stylinexpat

My sister's does the same thing. Happens in the morning when car is cold

That's definitely not normal.

And mine did it the whole ride home.

[XutvJet]

Have you tried actually looking for the source? It could something as simple as a pebble that's made it's way into the void between the exhaust pipe and tip, especially if the sound is coming from the passenger side where there is no exhaust valve.

[aerostar]

Originally Posted by XutvJet

Have you tried actually looking for the source? It could something as simple as a pebble that's made it's way into the void between the exhaust pipe and tip, especially if the sound is coming from the passenger side where there is no exhaust valve.

It's coming from the driver's side, I think.

I'm not digging around there. Gonna drop it off for warranty work and hope for a nice loaner.

[orangeglim]

Sounds like the exhaust flap. Mine has done this twice already and I just turned 11k miles on my 2016. The dealer has replaced the rear exhaust section both times. They ordered the wrong one the second time so my car actually had had four different rear exhausts on it so far. I will keep bringing it back under warranty if this keeps happening.

[kaputt]

Can the exhaust flap be removed on these cars?

[orangeglim]

Probably, its welded right into the tail pipe. You'd have to cut off the pipe, remove the flag, install some sort of extension and then weld it back on. I suppose you could just build a new tailpipe altogether too.

[jmwilson125]

Mine does this too, but not that bad yet.

[TajoMan]

I have same problem as well.
Mind started couple of weeks after the car was delivered.
It does not happen everyday. I've had my car about 3 month now and it happened about 4~5 times.
It makes rattle noise only when the car is cold and goes away in 1~2 minute.

It sounded like the exhaust valve flap is vibrating making that noise.

If it gets more frequent and start bothering me, I will take it to dealer.
They must have quick fix.

[aerostar]

Originally Posted by TajoMan

I have same problem as well.
Mind started couple of weeks after the car was delivered.
It does not happen everyday. I've had my car about 3 month now and it happened about 4~5 times.
It makes rattle noise only when the car is cold and goes away in 1~2 minute.

It sounded like the exhaust valve flap is vibrating making that noise.

If it gets more frequent and start bothering me, I will take it to dealer.
They must have quick fix.

Don't think so.

Have to cut out the exhaust to get to the valve.

Mine is stuck rattling regardless of whether or not the cars cold or warm.

I did a first gear pull with the windows down for shits and giggles and the rattling was insane. LOL

[XutvJet]

In most cases, the exhaust flap rattle is caused by a very small change in the tolerance of the flap bearing over heat cycles hence the reason you usually only hear it when the exhaust piping is stone cold. In most cases, the rattling is simply the flap assembly vibrating within the bearing ever so slightly as the exhaust vibrates heavily on startup. You can fix this noise yourself by either:

1) Spraying a thicker silicone lubricant on the exterior portions of the bearing, top and bottom. This usually quells the noise for 6 to 12 months. Takes 1 minute to accomplish.

2) Unplug the flap control plug while the flap is open and the car is off. In the open position, the flap is less prone to rattling on a cold start.

Another source I found could potentially be the lever arms and pins associated with the power unit that controls the flap operation. That too would be metal parts vibrating. In this case, a thick water proof and high temp lithium grease should solve it.

You can keep going back to BMW to get replacements, but it will eventually come back and once you're out of warranty, are you really going to replace the whole exhaust system? LOL BMW is not alone in this issue. EVERY car using these types of devices has reports of cold start rattles in the flap area.

[aerostar]

Originally Posted by XutvJet

In most cases, the exhaust flap rattle is caused by a very small change in the tolerance of the flap bearing over heat cycles hence the reason you usually only hear it when the exhaust piping is stone cold. In most cases, the rattling is simply the flap assembly vibrating within the bearing ever so slightly as the exhaust vibrates heavily on startup. You can fix this noise yourself by either:

1) Spraying a thicker silicone lubricant on the exterior portions of the bearing, top and bottom. This usually quells the noise for 6 to 12 months. Takes 1 minute to accomplish.

2) Unplug the flap control plug while the flap is open and the car is off. In the open position, the flap is less prone to rattling on a cold start.

Another source I found could potentially be the lever arms and pins associated with the power unit that controls the flap operation. That too would be metal parts vibrating. In this case, a thick water proof and high temp lithium grease should solve it.

You can keep going back to BMW to get replacements, but it will eventually come back and once you're out of warranty, are you really going to replace the whole exhaust system? LOL BMW is not alone in this issue. EVERY car using these types of devices has reports of cold start rattles in the flap area.

This isn't a cold start rattle. It's constant regardless of whether or not the car is hot or cold. And it's *loud*. You can hear it from pretty fkin far away.

[XutvJet]

I hear ya. I'm a DIY type though and will investigate issues even when the car is still under warranty. If it's a simple issue and it looks like I can fix it without potentially damaging the car in the process then I'll do it because I'd rather not spending 1+ hours of my time going to BMW, dropping off and picking up cars, sitting in waiting rooms, possibly rescheduling things to deal with the repair, etc. Even though my experiences with BMW service so far have been exceptional, my time is valuable.

[sternn]

had the same sound on my exhaust

was the "spring" on the exhaust flap

aerostar let them check that

[3rdcoast228i]

Originally Posted by XutvJet

I hear ya. I'm a DIY type though and will investigate issues even when the car is still under warranty. If it's a simple issue and it looks like I can fix it without potentially damaging the car in the process then I'll do it because I'd rather not spending 1+ hours of my time going to BMW, dropping off and picking up cars, sitting in waiting rooms, possibly rescheduling things to deal with the repair, etc. Even though my experiences with BMW service so far have been exceptional, my time is valuable.

So true, time is valuable! Running back and forth to the dealer is very time consuming.

Normally I have the problem diagnosed before it goes to the dealer. Why? Because automotive technicians are just like tech support. You have the low level guys that go through the normal motions, basically following a flow chart to diagnose the problem. And this is who you normally get when you first take it in. This guy does his best but you have to go through him to get to the high level tech.

For instance... my mother's Grand Cherokee battery died... charged it, dies again. Dad is busy and doesn't want to deal with it, but he looked at it enough to know something was draining power when the car was off. It's under warranty so he tells mom to take it to the dealer. She takes it and a few days later they call and she picks it up. Charged her $500 for a new battery and says it's fix. Gets it home and the battery dies again the next day. Dad has to deal with it now so he grabs the AMP meter and confirms that it's drawing power with the car off. A little more poking and figures out the clutch on the a/c compresser is staying engaged with the car off. A little Internet search reveals that these cars are known to have a power module go bad that causes this problem. Long story short, the module was under warranty but the battery wasn't. So he was out $500, a car, and a few days of his time. Because that's what happens when you get the low level guy.

[orangeglim]

I'm all for fixing stuff yourself, less chance of your car getting dinged up at the dealer. However, the first time mine did this was shortly after I ordered my MPE. It happened again after my MPE was delivered so I captured the sound on video using my iPhone. I took it over to the dealer and they said they needed to replace the rear section of the exhaust to fix it. So, I worked a deal out with them, they cut off the original exhaust and installed my newly purchased MPE instead of the warranty replacement. So, I got the MPE installed for $0 labor. And, I got the warrantied exhaust section, brand new, and an extra clamp to install it placed in my trunk. Not sure what I'm doing to do with it, but I still have it.

[aerostar]

Originally Posted by orangeglim

Sounds like the exhaust flap. Mine has done this twice already and I just turned 11k miles on my 2016. The dealer has replaced the rear exhaust section both times. They ordered the wrong one the second time so my car actually had had four different rear exhausts on it so far. I will keep bringing it back under warranty if this keeps happening.

How long did the repair take?

I'd assume a day to order the exhaust and another day to install so two days total?

Or were you in and out in a day?

I have a courtesy car for Friday. I'm wondering if it's going to extend into the weekend. If so, I'm going to be taking a long video of my exterior so I don't get dinged when I return the lease for a M3.