Exhaust rattle

[rwhgme]

I have a 2010 335i. On first startup and for a while after, the exhaust has a loud tinny rattle. I am sorry if this has been discussed before, but when I search for this on my iPad I find nothing. I will be taking it in for an iDrive driven "Service" appointment. The car has 29,100 miles. I have been changing the oil every 7500 miles. Just wondering if this issue has a name or explanation attached to it. Thank you all!

Never mind...Google to the rescue...

[rwhgme]

Just a quick update. My dealership says it is not a wastegate issue. It is a flap in the driver side muffler that changes the pitch on heavy acceleration. As I don't accelerate as hard as most, has anyone else heard of this?

[NFerber]

Yeah, that exhaust flap will sometime rattle on start-up. Look up the golf-tee mod, very easy way to disable the flap so it is always open. You get a slightly louder exhaust on startup due to the flap being open, and no more rattle.

[JinMao]

Not sure if this helps at all, but saw this in the faq for E90 cars on this site. (see quote pasted below).

I also drive 335i. Once in a while i hear a "tinny" sound. I've been told this this is not unusual when starting the car cold. I honestly don't hear it that often, but been told to expect it.

[QUOTE=Gig103;12010528]Q: Why is the exhaust coming out of only the right side?
[Originally posted by Rolyf]

In order to enhance the exhaust note emanating from the tailpipe(s), BMW has arranged a thermistor switched, electrically controlled, vacuum operated butterfly valve to close off the tailpipe on the driver's side while the engine warms up. This results in a more pleasant exhaust note when you are first pulling out of your neighborhood.

[rwhgme]

Thank you! Getting a new muffler that is being covered under warranty just did not know that these were so sophisticated.

[White94RX]

So now you're going to have a sawed off exhaust with a new muffler section clamped into place. That's why I hate doing them, and usually don't. I typically disconnect the vacuum line, or spot weld the flap open if the customer is okay with it. Noise is 100% eliminated, and no sawing off the exhaust.