Exhaust leak, possibly

[RPM90]

I was at a drive thru today next to a brick wall.
My window was down. As I waited I'm hearing my engine idle as it always has.

Then, I hear what sounds to me like distinct exhaust leak sound.
Hard to describe in words, but if you've heard one it's like a:
pft..pft..pft..pft, very rhythmic like an engine idle.
I gave the throttle a tap and it stop. It idled with no funny sound for about 20 seconds and then it came back.
Odd really. I'm not overly concerned just yet, but I'm keeping an ear on it.

Anyone hear or experience this with their 1's?

My 135i is a 2009 with about 18K miles.

[Kamal]

have you had any work done to your car that involved removing the exhaust? Easiest thing to do is jack the car up, have someone start the car and rev the engine and feel for a leak around the flanges/bolts.

[zkeeper]

But please do not get under the car without proper jack stands properly placed. Better yet, have it inspected on a proper rack. It sounds obvious but don't get under the car with merely a jack, even if it is one of the new heavy duty ones. A friend of mine lost his college age son who did this very thing, in the school dorm parking lot--because he did not want to spend the money at a local. Now of course, the expense is no longer an issue.

Have your dealer, or a decent indy, do a "stethoscope" test listen with the t headphones and probe tool that many have. It can find a leak, hiss, or obscure noise that you think is in one place, but is not. Sound travels and this device many can pinpoint pretty quick what or from where the noise orginates. It might be in the vanos tubes at top with air sensors. It could be an exhaust or intake leak. It might even in the air conditioner compressor.If you have replaced exhaust or any other intake devices, it could be coming from such...good luck and let us know whats a happen'.

[davidk]

I believe the sound you are hearing is the exhaust flapper valve located in one of your exhaust tips, and it is normal. You should be able to hear the same sound when you start the car and stand behind it, or just off to the side. I have a 2009 128, and it sounds like that, especially when cold. If you disconnect and plug the vacuum line going to it, it will resolve the problem, or at least help to identify the source of the noise. It is one reason I am seriously contemplating the BMW PE.

[RPM90]

Originally Posted by zkeeper

But please do not get under the car without proper jack stands properly placed. Better yet, have it inspected on a proper rack. It sounds obvious but don't get under the car with merely a jack, even if it is one of the new heavy duty ones. A friend of mine lost his college age son who did this very thing, in the school dorm parking lot--because he did not want to spend the money at a local. Now of course, the expense is no longer an issue.

Have your dealer, or a decent indy, do a "stethoscope" test listen with the t headphones and probe tool that many have. It can find a leak, hiss, or obscure noise that you think is in one place, but is not. Sound travels and this device many can pinpoint pretty quick what or from where the noise orginates. It might be in the vanos tubes at top with air sensors. It could be an exhaust or intake leak. It might even in the air conditioner compressor.If you have replaced exhaust or any other intake devices, it could be coming from such...good luck and let us know whats a happen'.

Sound advice.

I think it's good to post advice and information like this as other people will be helped as well.

Just to clarify, I'm mechanically inclined and have worked on cars for many years as I'm getting to be an "old fart".
You've pointed some of the same things I've been considering as well.

At this point it's still very intermittent. I let the car idle in the garage, for better acoustics, to hear the sound, but it didn't happen.
BTW, yes I left the garage door wide open to vent and it's 2.5 cars wide.

I don't think it's the exhaust flapper as it didn't sound like it was coming from the rear. But, I won't/can't rule it out completely as I've only heard the sound from the drivers seat while idling next to a brick wall.
Even though it sounded like it was coming from the front, that could be deceiving. That's why I tried to hear it today, but didn't.

The 135i hasn't had any work done to it that would lead me to think it might be related to a tech or their work causing it.
It might be just one of those things that just happens.

Thanks for the input guys, much appreciated.
If it gets worse and I find what it is, I'll update the thread.

[RPM90]

Originally Posted by davidk

I believe the sound you are hearing is the exhaust flapper valve located in one of your exhaust tips, and it is normal. You should be able to hear the same sound when you start the car and stand behind it, or just off to the side. I have a 2009 128, and it sounds like that, especially when cold. If you disconnect and plug the vacuum line going to it, it will resolve the problem, or at least help to identify the source of the noise. It is one reason I am seriously contemplating the BMW PE.

I'll keep this in mind, thanks.

I don't think it's that valve as I've been behind the car on cold start on very cold and very warm days, and my exhaust has never had a pronounced "chuffing" sound from that area like what I heard the other day.

I won't discount it though. Good suggestion, thanks.