2014 M235i - Weird exhaust rattle for 10-20 seconds on cold start?

Vancity128guy · 11-26-2019, 02:45 PM

Hi all,

I have a 2014 M235i with 55K KM's on the clock and it's been great thus far. I bought it pre-owned a few months ago. Unfortunately, there isn't any warranty left which is why I am asking here... Additionally, about two months ago I was rear ended by an idiot at a red light, relatively slow speed, but required the bumper, reinforcement bar to be replaced. Not sure if this issue is related to that...

The last two days it's been quite cold here, and I noticed after letting the car sit overnight, when I start it in the morning, there is a fairly loud rattle coming from the driver side exhaust area. It's pronounced when the RPMs get above 1000 on the cold start. After that, the sound goes away quickly (within 20 seconds) and it sounds normal again.

It's quite embarrassing sound to say the least. I have read about the exhaust flap/valve being an issue, but everything I read says that the sound would be constant if this was the issue.

Does anyone have any ideas what this could be?

accs · 11-26-2019, 03:12 PM

You could try unplugging the valve and see if that fixes it.

Vancity128guy · 11-27-2019, 02:31 PM

Quote:

Originally Posted by RyonC

You could try unplugging the valve and see if that fixes it.

OK might give this a try.

Anyone else experience this issue?

BEM-S4 · 11-27-2019, 03:35 PM

Valve is likely bad and needs to be replaced. 5 minute job. They didn't even roll mine into the shop did it right in the intake bay.

XutvJet · 11-28-2019, 12:54 PM

Don't bother replacing the valve as there is no long term fix. It always comes back. A simply fix is shooting some silicone penetrating oil around the external portion of valve assembly and it's bearings. The rattle will disappear for a good while. Mine rattles on and off since about 6 months after I got the car new back in Feb 2016. A quick shot of penetrating oil will quit it for 6+ months.

Ron Jeffries · 11-28-2019, 02:38 PM

You guys are so lucky to have a flap. The 2018 doesn't even get a flap.

ljason8eg · 11-28-2019, 04:22 PM

Quote:

Originally Posted by XutvJet

Don't bother replacing the valve as there is no long term fix. It always comes back. A simply fix is shooting some silicone penetrating oil around the external portion of valve assembly and it's bearings. The rattle will disappear for a good while. Mine rattles on and off since about 6 months after I got the car new back in Feb 2016. A quick shot of penetrating oil will quit it for 6+ months.

Hey thanks for this tip. I recently got the dreaded rattle but noticed the fixing bow was still in place and the valve operates normally and when the valve is open the rattle disappears.

I'll try the silicone penetrating oil.

accs · 11-28-2019, 09:30 PM

Quote:

Originally Posted by Ron Jeffries

You guys are so lucky to have a flap. The 2018 doesn't even get a flap.

Not rly useful. Car isn't much quieter with it closed... Probably why they took it out

Climate Changer · 11-29-2019, 12:38 PM

My 2018 230i has the flap. It rattled so much and the fixing bow was replaced and still rattled.

My fix= Muffler delete no more rattle only pops and burbles.

9t2hoo · 11-29-2019, 01:28 PM

I switched to the Remus exhaust and no more rattle. I hope it’s more durable than the OEM flap.

Ron Jeffries · 11-30-2019, 09:10 AM

I want the car noisier, not quieter. My 135IS had so much more snap, crackle, and pop. Took me back to my teenage years.

Poochie · 11-30-2019, 09:18 AM

Quote:

Originally Posted by XutvJet

Don't bother replacing the valve as there is no long term fix. It always comes back. A simply fix is shooting some silicone penetrating oil around the external portion of valve assembly and it's bearings. The rattle will disappear for a good while. Mine rattles on and off since about 6 months after I got the car new back in Feb 2016. A quick shot of penetrating oil will quit it for 6+ months.

I thought about this bandaid fix but I figure the hot exhaust would just dissipate the lubricant.

Roughly, how long it takes before oil wears out and noise reappears?

DaleHeinz · 12-01-2019, 11:43 AM

I've already had 2 valves replaced in my '17 240. The rattle is very annoying and gets worse over time. Both times the dealer covered the replacement, and didn't care that it was out of warranty for the second one. I get about 30K miles out of one before they go. Next one I may do myself if they don't cover it.

B58togo · 12-03-2019, 12:20 PM

Quote:

Originally Posted by 9t2hoo

I switched to the Remus exhaust and no more rattle. I hope it’s more durable than the OEM flap.

I did this too. Awesome exhaust and not a bad price either. Relatively speaking of course.

11-26-2019, 02:45 PM	#1
Vancity128guy New Member 4 Rep 23 Posts Drives: 2011 128i Join Date: May 2017 Location: Vancouver iTrader: (0)	2014 M235i - Weird exhaust rattle for 10-20 seconds on cold start? Hi all, I have a 2014 M235i with 55K KM's on the clock and it's been great thus far. I bought it pre-owned a few months ago. Unfortunately, there isn't any warranty left which is why I am asking here... Additionally, about two months ago I was rear ended by an idiot at a red light, relatively slow speed, but required the bumper, reinforcement bar to be replaced. Not sure if this issue is related to that... The last two days it's been quite cold here, and I noticed after letting the car sit overnight, when I start it in the morning, there is a fairly loud rattle coming from the driver side exhaust area. It's pronounced when the RPMs get above 1000 on the cold start. After that, the sound goes away quickly (within 20 seconds) and it sounds normal again. It's quite embarrassing sound to say the least. I have read about the exhaust flap/valve being an issue, but everything I read says that the sound would be constant if this was the issue. Does anyone have any ideas what this could be? Last edited by Vancity128guy; 11-26-2019 at 02:55 PM..
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11-26-2019, 03:12 PM	#2
accs Private First Class 25 Rep 142 Posts Drives: M235i Join Date: Nov 2018 Location: Van iTrader: (0)	You could try unplugging the valve and see if that fixes it.
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11-27-2019, 03:35 PM	#4
BEM-S4 Major General 4515 Rep 8,942 Posts Drives: Dinan M235, Dinan Sport Wagon Join Date: Oct 2012 Location: Philadelphia iTrader: (5)	Valve is likely bad and needs to be replaced. 5 minute job. They didn't even roll mine into the shop did it right in the intake bay. __________________ 2022 Macan S 2016 F31 328i xDrive Sport Wagon 2006 E46 330ci ZHP Convertible
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11-28-2019, 12:54 PM	#5
XutvJet Major General 5538 Rep 5,364 Posts Drives: 2011 Cayman Base, 2016 M235 Join Date: Mar 2016 Location: Kansas City iTrader: (-1)	Don't bother replacing the valve as there is no long term fix. It always comes back. A simply fix is shooting some silicone penetrating oil around the external portion of valve assembly and it's bearings. The rattle will disappear for a good while. Mine rattles on and off since about 6 months after I got the car new back in Feb 2016. A quick shot of penetrating oil will quit it for 6+ months. __________________ The forest was shrinking, but the Trees kept voting for the Axe, for the Axe was clever and convinced the Trees that because his handle was made of wood, he was one of them.
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11-28-2019, 02:38 PM	#6
Ron Jeffries Old Member. Old in general, actually. 386 Rep 889 Posts Drives: 2018 M240i xDrive convertible Join Date: Feb 2013 Location: Michigan iTrader: (0)	You guys are so lucky to have a flap. The 2018 doesn't even get a flap.
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11-29-2019, 12:38 PM	#9
Climate Changer Second Lieutenant 109 Rep 278 Posts Drives: 2018 230i xdrive convertible Join Date: Oct 2018 Location: New York iTrader: (0) Garage List 2018 230i xdrive co ... [0.00] 2019 x3 [0.00]	My 2018 230i has the flap. It rattled so much and the fixing bow was replaced and still rattled. My fix= Muffler delete no more rattle only pops and burbles.
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11-29-2019, 01:28 PM	#10
9t2hoo Private First Class 66 Rep 133 Posts Drives: 2024 Cayman S Join Date: Mar 2008 Location: Washington, D.C. iTrader: (0)	I switched to the Remus exhaust and no more rattle. I hope it’s more durable than the OEM flap.
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11-30-2019, 09:10 AM	#11
Ron Jeffries Old Member. Old in general, actually. 386 Rep 889 Posts Drives: 2018 M240i xDrive convertible Join Date: Feb 2013 Location: Michigan iTrader: (0)	I want the car noisier, not quieter. My 135IS had so much more snap, crackle, and pop. Took me back to my teenage years.
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12-01-2019, 11:43 AM	#13
DaleHeinz First Lieutenant 221 Rep 314 Posts Drives: M240Xi Estoril Blue Join Date: Apr 2017 Location: Washington DC area iTrader: (1)	I've already had 2 valves replaced in my '17 240. The rattle is very annoying and gets worse over time. Both times the dealer covered the replacement, and didn't care that it was out of warranty for the second one. I get about 30K miles out of one before they go. Next one I may do myself if they don't cover it.
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