Help! - Strange noise from rear of car when lifting off throttle

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platinum70
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Help! - Strange noise from rear of car when lifting off throttle

Post by platinum70 » Wed Mar 21, 2018 8:55 pm

I have a 2016 M140i that has developed a rather strange fault today.

I often hear a sound from what seems to be the rear where something seems to be closing when crawling along a low speed. A bit like the sound some cars make when the air vent flap at the front closes when you are crawling in traffic to prevent fumes coming through the air system.

But today I then heard another noise following this sound which is hard to explain. It is almost like a mechanical whirring where something is trying to engage or open and it only does it (or at least I can only hear it) from around when coming off throttle below 40mph. Almost ratchet like for want of a better word. I have a BCS Powervalve exhaust so it can't be the exhaust flap issue mentioned on here before.

Does anyone have any suggestions or ideas as to what this could be??
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Re: Help! - Strange noise from rear of car when lifting off throttle

Post by Bmw_ire_2012 » Thu Mar 22, 2018 12:41 am

platinum70 wrote:
Wed Mar 21, 2018 8:55 pm
I have a 2016 M140i that has developed a rather strange fault today.

I often hear a sound from what seems to be the rear where something seems to be closing when crawling along a low speed. A bit like the sound some cars make when the air vent flap at the front closes when you are crawling in traffic to prevent fumes coming through the air system.

But today I then heard another noise following this sound which is hard to explain. It is almost like a mechanical whirring where something is trying to engage or open and it only does it (or at least I can only hear it) from around when coming off throttle below 40mph. Almost ratchet like for want of a better word. I have a BCS Powervalve exhaust so it can't be the exhaust flap issue mentioned on here before.

Does anyone have any suggestions or ideas as to what this could be??
Only thing that springs to mind is the little connection for the old exhaust system, check that hasn't came loose.
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Re: Help! - Strange noise from rear of car when lifting off throttle

Post by platinum70 » Thu Mar 22, 2018 1:22 am

Only thing that springs to mind is the little connection for the old exhaust system, check that hasn't came loose.
[/quote]

Where do I look for that? Appreciate your help and thanks for the reply
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Re: Help! - Strange noise from rear of car when lifting off throttle

Post by platinum70 » Thu Mar 22, 2018 1:24 am

I wondered if it was the fuel pump
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Re: Help! - Strange noise from rear of car when lifting off throttle

Post by marco_polo » Thu Mar 22, 2018 8:04 am

Is it the BCS valve closing as the boost drops? How often do you clean the salt off, lubricate it, etc?
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Re: Help! - Strange noise from rear of car when lifting off throttle

Post by Bmw_ire_2012 » Thu Mar 22, 2018 8:08 am

I've the BCS and never heard this, the exhaust is to loud to hear anything else when you're on it lol.

Check this out from a form member on what I was taking about, might not be that but worth a look.

https://www.youtube.com/watch?v=H6O4Grdxjhs
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Re: Help! - Strange noise from rear of car when lifting off throttle

Post by marco_polo » Thu Mar 22, 2018 8:14 am

Bmw_ire_2012 wrote:
Thu Mar 22, 2018 8:08 am
I've the BCS and never heard this, the exhaust is to loud to hear anything else when you're on it lol.
But this is when he's off it, crawling at low speed.
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Re: Help! - Strange noise from rear of car when lifting off throttle

Post by Bmw_ire_2012 » Thu Mar 22, 2018 8:17 am

marco_polo wrote:
Thu Mar 22, 2018 8:14 am
Bmw_ire_2012 wrote:
Thu Mar 22, 2018 8:08 am
I've the BCS and never heard this, the exhaust is to loud to hear anything else when you're on it lol.
But this is when he's off it, crawling at low speed.
I see, the vale only opens when you're on it so don't think it's the vale could be wrong, The first thing that I though it might be is the exhaust actuator since it's disconnected to install the BCS, other than that I'd have no idea :lol:
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Re: Help! - Strange noise from rear of car when lifting off throttle

Post by marco_polo » Thu Mar 22, 2018 8:22 am

So the valve only opens when you're on it, when does it close? Presumably when coming off the throttle, per the OP's problem?

I've not got a BCS, but I'm assuming the valve is opened by turbo boost pressure, and closed by a spring?
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Re: Help! - Strange noise from rear of car when lifting off throttle

Post by Bmw_ire_2012 » Thu Mar 22, 2018 8:34 am

Yes it only opens up when you're on it, closes when you are not. No idea if it's closed by a spring again or not Marco, just that it's operated by a boost hoes.
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Re: Help! - Strange noise from rear of car when lifting off throttle

Post by platinum70 » Thu Mar 22, 2018 10:46 am

marco_polo wrote:
Thu Mar 22, 2018 8:04 am
Is it the BCS valve closing as the boost drops? How often do you clean the salt off, lubricate it, etc?
Marco - I wasn't aware you needed to. I will have a look but may well call Nigel first just to make sure I am doing it all correctly. If the noise was th fuel pump would I have other issues?
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Re: Help! - Strange noise from rear of car when lifting off throttle

Post by marco_polo » Thu Mar 22, 2018 11:18 am

The valve and actuator lives unprotected, in one the nastiest saltiest environments possible. I'd be surprised if it didn't need a little sensible preventative maintenance occasionally? If it contains rubber seals, I'd be giving it a quick clean then spray with a silicone grease?

There aren't any reports of M140i low pressure fuel pump issues, and they'd usually just stop working rather than making sporadic mechanical valve noises. I guess it's not impossible, but would be low on my list of things to check.
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Re: Help! - Strange noise from rear of car when lifting off throttle

Post by platinum70 » Thu Mar 22, 2018 11:20 am

Spoken to Nigel and the other possibility is the boost hose to the exhaust valve. Need to get underneath and have a look. Thanks for the responses folks...
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Re: Help! - Strange noise from rear of car when lifting off throttle

Post by KR15 » Thu Mar 22, 2018 12:17 pm

Bmw_ire_2012 wrote:I've the BCS and never heard this, the exhaust is to loud to hear anything else when you're on it lol.

Check this out from a form member on what I was taking about, might not be that but worth a look.

https://www.youtube.com/watch?v=H6O4Grdxjhs
Off topic but whatever happened to Blowsy? He was quite active on the forum and started posting regular videos to YouTube but then nothing for 9 months (according to YT)....

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Re: Help! - Strange noise from rear of car when lifting off throttle

Post by Jahjaman » Thu Mar 22, 2018 12:25 pm

It wouldn't be the BCS valve - it requires a fair amount of boost to open up and it will close off as soon as you step off the full boost.

Even mild throttle won't open the BCS valve.
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