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      12-30-2015, 06:29 AM   #1
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Exhaust rattle on 335i

Hey guys

Go easy on me, my first post here

Recently took ownership of my first BMW.. an 09 e92 sapphire black 335i M-sport. Absolutely loving it so far, I believe its still completely stock so just enjoying the power it currently has before the mod bug hits.

Had it for a month or two so far and seems in good nick, however I've noticed an ugly sound coming from I think the left side of the car which happens on cold starts and also while driving. I've done a bit of research and it seems to be the exhaust.. sounds exactly like this but goes for about 10-15 seconds on cold start then disappears:




Is there a way to fix this? If i get a new exhaust will the noise disappear? Is this a good excuse to get a new exhaust? lol..
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      12-30-2015, 07:10 AM   #2
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very common, BMW sells a replacement muffeler that requires you to cut and clamp the new one in.

That exhaust flap on the side becomes weak and starts rattling, right side doesn't have this.

You can either replace just the one mufflero n that side or get a new after market one. My favorite is still the BMW Performance exhaust (no flap)
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      12-30-2015, 07:31 AM   #3
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Thanks for the response

Weird how it only happens on the left side..

Anyway, might just persist with it for now and then go with the BMW performance exhaust. I was considering that regardless, might help make the decision a bit easier.
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      12-30-2015, 07:56 AM   #4
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Quote:
Originally Posted by jus335 View Post
Thanks for the response

Weird how it only happens on the left side..

Anyway, might just persist with it for now and then go with the BMW performance exhaust. I was considering that regardless, might help make the decision a bit easier.
It only happens in the left because there is only a flap in the left.

On cold starts and until the engine warms up the car keeps it closed to help warm up the cats believe. Getting a a JB4 or doing the gold tee mod will keep it open, also another 'mod' you can disconnect the power cable in the boot.
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      12-30-2015, 08:06 AM   #5
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Quote:
Originally Posted by EB89 View Post
It only happens in the left because there is only a flap in the left.

On cold starts and until the engine warms up the car keeps it closed to help warm up the cats believe. Getting a a JB4 or doing the gold tee mod will keep it open, also another 'mod' you can disconnect the power cable in the boot.
Ah right, well there you go. Still have a lot to learn about this car, thanks for the tips.

btw, I've seen your car a couple of times around town, I recognise your plate. I'm actually from Wollongong

Looks really nice mate, you don't see many 335's down here
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      12-30-2015, 04:29 PM   #6
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in the boot on the left hand side just under the tail light. you will see a plug. unplug it. problem solved ;]
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      12-30-2015, 06:44 PM   #7
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Quote:
Originally Posted by naynay View Post
in the boot on the left hand side just under the tail light. you will see a plug. unplug it. problem solved ;]
Is this ok to do? I've read it causes 'hidden' error codes but I assume this is harmless and can be fixed. Other than that its ok?
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      12-30-2015, 06:49 PM   #8
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Originally Posted by jus335 View Post
Is this ok to do? I've read it causes 'hidden' error codes but I assume this is harmless and can be fixed. Other than that its ok?
I did a lot of reading on it, the flaps are closed for a reason, to help parts of the car warm up, so there "might" be some negative effects, but no one really knows, most people do it for the extra noise but then a lot say you can barely hear anything, then there are mixed reports in error codes showing.

I came to the consulsion that it's not worth it, I'm getting the JB4 to do it.
If you do you should allow extra time for your car to warm up on cold starts.
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      12-30-2015, 07:03 PM   #9
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Quote:
Originally Posted by EB89 View Post
I did a lot of reading on it, the flaps are closed for a reason, to help parts of the car warm up, so there "might" be some negative effects, but no one really knows, most people do it for the extra noise but then a lot say you can barely hear anything, then there are mixed reports in error codes showing.

I came to the consulsion that it's not worth it, I'm getting the JB4 to do it.
If you do you should allow extra time for your car to warm up on cold starts.
"parts of the car"
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      12-30-2015, 07:30 PM   #10
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Quote:
Originally Posted by naynay
in the boot on the left hand side just under the tail light. you will see a plug. unplug it. problem solved ;]
Exactly this.
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      12-30-2015, 07:50 PM   #11
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Quote:
Originally Posted by EB89 View Post
On cold starts and until the engine warms up the car keeps it closed to help warm up the cats believe.
The car holds the wastegates open a lot more for cold starts and runs different vanos settings to warm the cats up - default setting for cold start is 65 seconds. Because of this, the car runs really loud at cold start, and closing the flap helps this. For those who have kittyless DP's you can remove the cold start setting through MHD.

Having the flap open doesn't harm anything and doesn't help warm up cats faster. Just a bit more noise.
If you do it by unplugging the wire in the boot, you will get a shadow code, that is all.
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      12-30-2015, 07:52 PM   #12
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Quote:
Originally Posted by jus335 View Post
Is this ok to do? I've read it causes 'hidden' error codes but I assume this is harmless and can be fixed. Other than that its ok?
Yes it throws a shadow code, but that is harmless. You have to scan it to read it.
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      12-30-2015, 07:56 PM   #13
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Quote:
Originally Posted by EB89 View Post
If you do you should allow extra time for your car to warm up on cold starts.
Warming the cats up improves emissions.

Having the flap open doesn't mean you need extra time to warm up.

But it is always good to let your car warm up before giving it the berries.
Best to warm up with gentle driving, but not idling. Oil is more effective when warm and taking a long time to warm up actually promotes engine wear.
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      12-30-2015, 08:04 PM   #14
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Quote:
Originally Posted by harms View Post
Warming the cats up improves emissions.

Having the flap open doesn't mean you need extra time to warm up.

But it is always good to let your car warm up before giving it the berries.
Best to warm up with gentle driving, but not idling. Oil is more effective when warm and taking a long time to warm up actually promotes engine wear.
Ok then fair enough
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      12-30-2015, 08:06 PM   #15
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Quote:
Originally Posted by harms View Post
The car holds the wastegates open a lot more for cold starts and runs different vanos settings to warm the cats up - default setting for cold start is 65 seconds. Because of this, the car runs really loud at cold start, and closing the flap helps this. For those who have kittyless DP's you can remove the cold start setting through MHD.

Having the flap open doesn't harm anything and doesn't help warm up cats faster. Just a bit more noise.
If you do it by unplugging the wire in the boot, you will get a shadow code, that is all.
So the only reason the flap exists is to stop noise?
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      12-31-2015, 12:37 AM   #16
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I have the same rattle on my 335i. From what I've read on various forums it looks like this flap is purely for noise reduction.
The flap actually remains closed if you are just idling or cruising with low RPMs. But once you press the pedal to the metal it opens.

I did the "unplug connector in the boot" version of the golf tee mod and noticed that the exhaust sounds a bit louder during regular driving. And I think I get more "pops" when decelerating.

Here's a good guide on how to do it (takes 2 minutes) to do:
www.e90post.com/forums/showthread.php?t=80661
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      12-31-2015, 01:25 AM   #17
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Quote:
Originally Posted by Midlife_C View Post
I have the same rattle on my 335i. From what I've read on various forums it looks like this flap is purely for noise reduction.
The flap actually remains closed if you are just idling or cruising with low RPMs. But once you press the pedal to the metal it opens.

I did the "unplug connector in the boot" version of the golf tee mod and noticed that the exhaust sounds a bit louder during regular driving. And I think I get more "pops" when decelerating.

Here's a good guide on how to do it (takes 2 minutes) to do:
www.e90post.com/forums/showthread.php?t=80661
Yeah read a bit of this thread earlier today. Has yours rattled at all after you unplugged it?
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      12-31-2015, 01:50 AM   #18
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The rattle has completely gone after I unplugged it.
And came back once I reconnected the plug.

But now I have JB4 that allows to have the flap set to open.
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      12-31-2015, 01:58 AM   #19
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Will have to try this.

Thanks to all for the advice
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      12-31-2015, 07:24 AM   #20
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i have the rattle and the golf tee mod doesn't do a thing. The rattle comes from the actuator arm where it meets the valve pin im pretty certain. If you go under the car and give the actuator arm a shake you will see what i mean. The only way to fix it would to be either weld the arm permanently, replace the valve with a straight pipe to the tip or replace the muffler.
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      12-31-2015, 06:13 PM   #21
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I have it and the rattle exists with the vacuum or wire in or removed.
Its the pin shaking.
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      12-31-2015, 06:21 PM   #22
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There are no hidden faults, the performance exhaust doesn't have a dlap and requires it to be plugged. There is no effect to your vehicle.
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