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      03-10-2012, 06:30 PM   #1
Jax543210
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Z4 rare problem? engine noise from firewall; dash/footwell

Z4 2007 40k miles (posting this issue on a few different BMW forums as it seems to be rare and after lots of searching have not found any fixes)

Day 1 relatively loud fan noise coming from behind/under/inside driver's side dash near headlight switch. I made sure the air conditioning and fan controls were off. Never really heard this particular fan noise before; I'm assuming it's the e-box fan. Also, no air flow was coming out of that driver's side vent and its definitely not the same fan noise and origin as the climate control fan.

Day 2 The fan noise is gone. I can now hear engine noise coming from the same general area of the dash. Louder than engine noise anywhere else in the cabin of the car. I'd describe the engine noise sounding like a vent or flap has opened up between the inside of the dash/driver footwell and the engine compartment and is letting noise through.

Day3 same noise coming through driver side section of dash. Sound can't be heard with windows down. Sound can best be heard with engine RPM's over 2k+; gas pedal engaged while driving; and windows up.

There are no strange noises coming from the engine with the hood open. The engine noise coming through the firewall into the cabin is just louder than normal in that area of the dash. Sounds kind of like the door or window was left open, but the door and window are shut and the noise isn't coming from the door or window but the dash area.

Does anyone know if there is a vent or opening in that area of the dash/footwell that perhaps allows the e-box fan to ventilate the e-box and if this vent/flap perhaps got itself stuck open?
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      03-11-2012, 01:04 PM   #2
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Don't know what model you have, but maybe if fitted it's the sound generator your hearing, maybe the tubing has popped out the grommet on the fire wall.
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      03-11-2012, 01:08 PM   #3
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Quote:
Originally Posted by Flying Scotsman View Post
Don't know what model you have, but maybe if fitted it's the sound generator your hearing, maybe the tubing has popped out the grommet on the fire wall.
Yup. Probably that.
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      03-11-2012, 03:43 PM   #4
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Good suggestion.
Z4 3.0 si
The Sound generator pipe is securely plugged into the firewall.
No visible cracks or damage in the piping either.

Problem persists.

Anyone know where the e-box fan is and how it vents or draws air?
Attached is a picture of it.

It looks like it draws air from the footwell and out to the engine compartment?
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      03-11-2012, 04:10 PM   #5
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I think e-box might be the same a the control unit box that's found opposite the driver in the engine bay. I wonder if it gets vented by the e-box fan that seems to be located in the cabin or air from the cabin?
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      03-11-2012, 08:30 PM   #6
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Quote:
Originally Posted by Jax543210 View Post
I think e-box might be the same a the control unit box that's found opposite the driver in the engine bay. I wonder if it gets vented by the e-box fan that seems to be located in the cabin or air from the cabin?


E-box fan S54


The E-box fan is fitted in the area of the MSS70 control unit and it cools the control unit. This is intended to exclude temperature-related sources of error in the function of the control unit.
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      03-12-2012, 06:49 PM   #7
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Quote:
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E-box fan S54


The E-box fan is fitted in the area of the MSS70 control unit and it cools the control unit. This is intended to exclude temperature-related sources of error in the function of the control unit.
Hi Ron,
What a weird problem. I'd take it into the dealer, but I bet they will not find anything as they are not good a trouble shooting noises that are uncommon and therefore probably claim it's a normal sound, even though it only started the other day, 4 years and 40k miles later.

Do you know how I can get to this fan and where it vents as well as gets fresh air from?

I'm out of ideas as to why all of a sudden it sounds like there is a small door open in my driver's side dash.

Today I disconnected and removed the pipe that runs from the sound generator to the firewall; plugged up the hole in the firewall with a microfiber towel; and did the same to the sound generator. Unfortunately, the noise when I accelerate is still there.

The noise kind of sounds like an electronic whirring sound, somewhere in-between fluid rushing at high pressure through a rubber hose and a CD player searching for a track to play, but it's hard to describe. Someone else may say it sounds like a tiny belt slipping. I can make the noise pulse by pushing the accelerator and making the RPM swing between 2k and 4k rpm. Above those RPM there is too much other noise drowning it out.
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      03-13-2012, 12:00 AM   #8
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Quote:
Originally Posted by Jax543210 View Post
Hi Ron,
What a weird problem. I'd take it into the dealer, but I bet they will not find anything as they are not good a trouble shooting noises that are uncommon and therefore probably claim it's a normal sound, even though it only started the other day, 4 years and 40k miles later.

Do you know how I can get to this fan and where it vents as well as gets fresh air from?

I'm out of ideas as to why all of a sudden it sounds like there is a small door open in my driver's side dash.

Today I disconnected and removed the pipe that runs from the sound generator to the firewall; plugged up the hole in the firewall with a microfiber towel; and did the same to the sound generator. Unfortunately, the noise when I accelerate is still there.

The noise kind of sounds like an electronic whirring sound, somewhere in-between fluid rushing at high pressure through a rubber hose and a CD player searching for a track to play, but it's hard to describe. Someone else may say it sounds like a tiny belt slipping. I can make the noise pulse by pushing the accelerator and making the RPM swing between 2k and 4k rpm. Above those RPM there is too much other noise drowning it out.
I thought it was a M coupe in #1 .

Sorry.
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      03-13-2012, 05:13 PM   #9
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I took a video of the sound/noise. Doing the actual filming made me analyze how the noise appears all over again. [sadly the audio quality that my smartphone produced wasn't good enough to pick up the noise ]

The noise can not be heard when car is in park and the engine is rev'd, inside or outside of cabin.

The noise is not directly linked to RPM. If I coast at 2-3+ RPM the sound doesn't exist.

However, if I push the accelerator, while RPMs are above 2k, while driving, then the noise appears. I can make the noise come and go as I push and let go of the accelerator above 2k RPM while driving.
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      03-13-2012, 08:52 PM   #10
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One other question. I love the stereo but there's no sat radio or input. How can either or both of these be added?
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      03-13-2012, 08:53 PM   #11
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Sorry...using the iPad app and posted that to the wrong thread.
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      03-14-2012, 06:57 PM   #12
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In researching this issue I found pictures of someone removing their DME / ECU from the box that sits in front of the driver in the engine bay. In the picture the box had a small opening that allows air to be pumped into it from what I'm assuming is the cabin.

Does anyone know if the ECU / DME emits very low decibels of electrical noise or has anything to do with gas pedal input? I plan on pulling off the plastic cover above the pedals to see if I can see what's feeding this box and maybe add some dynamat or similar sound blocking product without blocking any vital airflow.

Last edited by Jax543210; 03-14-2012 at 06:58 PM. Reason: spelling error
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      03-14-2012, 07:49 PM   #13
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Quote:
Originally Posted by Jax543210 View Post
I took a video of the sound/noise. Doing the actual filming made me analyze how the noise appears all over again. [sadly the audio quality that my smartphone produced wasn't good enough to pick up the noise ]

The noise can not be heard when car is in park and the engine is rev'd, inside or outside of cabin.

The noise is not directly linked to RPM. If I coast at 2-3+ RPM the sound doesn't exist.

However, if I push the accelerator, while RPMs are above 2k, while driving, then the noise appears. I can make the noise come and go as I push and let go of the accelerator above 2k RPM while driving.
After following this thread awhile, and looking at posts that have been added to pre-existing threads on "odd noises", I doubt it's the ECU. I'd bet that's just where the sound is focused, not the source of the sound. Just like rattles, tracking down sound sources is a tough nut to crack.

The noise is there when the engine is under load. This points to it being an air intake related (which includes vacuum parts of the system) or exhaust related: a leak of some kind. If it were some ECU fan or some other fan that would not be present upon acceleration only.

Outside of the brake booster I'm not sure what other systems use vacuum in our cars. But those systems need a check. Then there's the air intake system. Cracks, leaks, etc? Finally, exhaust. Leaks, etc.

The other possibility is that a small demon or gremlin has made a home in your firewall. I hear that's pretty tough to address without a pretty extensive rebuild and a lot of spells. So I really hope it's just a leak. So much easier to deal with than all the all the messy spells and welding.
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      03-15-2012, 05:32 PM   #14
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Thanks Finnegan.

To make things more complicated when I start the car it sounds like my door or window is open, but it's coming from the driver's footwell.
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      03-15-2012, 06:15 PM   #15
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Take the airbox to intake hose off and flex it your hands to look for cracks, That is what it sounds like to me.

When you first start it you hear it untill the vacuum pulls the cracks closed, then anything under load it opens/pulls air through the cracks? Just a thought.
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      03-20-2012, 03:53 PM   #16
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Thanks for all the advice. Took the whole air induction piping out. Easy enough. Good news is the pipes were all in good condition including the parts with the folds for the corners. Bad news is the noise I'm hearing in the cabin is something as of yet unknown.
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      03-20-2012, 08:55 PM   #17
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Funny thing....today I was driving and although I read this thread....I never noticed any noise at all...however today I had the radio shut off (ipod was left at home and I hate normal radio).

I heard a slight whistle as I accelerated...not a huge sound...but subtle...but it is there. Might this be a small crack in some air hose as other mentioned? Where would I look first...ideas? Pics?

I figure any pics or suggestions might also help the OP.

Thanks.
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      03-21-2012, 06:24 PM   #18
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See this thread for the cause of my issues.
http://www.zpost.com/forums/showthread.php?t=664934
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