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      10-07-2015, 07:47 AM   #1
Alan l.
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Hissing/air sound by rear suspension?

Do you guys notice a hissing/air sound coming from the rear wheel area? I was bending down looking at something on my driverside rear wheel and noticed a hissing sound coming from the car. At first I thought crap did i get a nail in the tire but I didn't. Tire is fine, Adaptive M air suspension isn't sagging or anything. To be honest the sound could have been there all along but i just noticed this.....

Anyone else?

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      10-07-2015, 08:15 AM   #2
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I don't notice it, is it a constant sound?. Perhaps it's the high pressure fuel pump?
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      10-07-2015, 08:19 AM   #3
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its a constant sound. Maybe i'm just being paranoid lol
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      10-07-2015, 10:24 AM   #4
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I'll have to check mine...but nothing that I've noticed.
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      10-07-2015, 11:06 AM   #5
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I get a hissing for only a few seconds after unlocking the car when it's been "asleep." I just thought it was normal with the adaptive m suspension/rear bags adjusting
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      10-07-2015, 11:15 AM   #6
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I get that too but this was after me driving for a bit. let me check it out again. possible that the air suspension is constantly adjusting the back height based on load/driving situations.

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      10-07-2015, 11:29 AM   #7
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Quote:
Originally Posted by Kief View Post
I get a hissing for only a few seconds after unlocking the car when it's been "asleep." I just thought it was normal with the adaptive m suspension/rear bags adjusting
High Pressure Fuel Pump, priming the fuel system.
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      10-07-2015, 12:56 PM   #8
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Quote:
Originally Posted by Kief
I get a hissing for only a few seconds after unlocking the car when it's been "asleep." I just thought it was normal with the adaptive m suspension/rear bags adjusting
I hear the same when unlocking the car but I have the standard suspension
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      10-07-2015, 01:14 PM   #9
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Quote:
Originally Posted by JNoSol View Post
High Pressure Fuel Pump, priming the fuel system.
Doh, and I'm use to that. It just sounds much louder in the F15 and I assumed it was related to the suspension. Funny how I don't even notice the priming with my M4, but I have in my previous bimmers. Thanks

Quote:
Originally Posted by RR-NYC View Post
I hear the same when unlocking the car but I have the standard suspension
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      10-07-2015, 01:17 PM   #10
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Quote:
Originally Posted by Kief View Post
Doh, and I'm use to that. It just sounds much louder in the F15 and I assumed it was related to the suspension. Funny how I don't even notice the priming with my M4, but I have in my previous bimmers. Thanks
It's probably because it's higher off the ground, easier to hear.
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      10-07-2015, 01:45 PM   #11
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I do not know how you drive, but I drive with increased music to the max and also banging bass else hear
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      02-24-2019, 01:51 PM   #12
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Sorry to bring up a old thread but I couldnt find anything else. As of last night I've been hearing a slight hissing noise while idling at a light or slowing down to a light. It sounds like its coming from behind me on the driver side door, it's very faint but its definitely there. Im not sure if this is normal but today I looked around the car for the noise and closest duplicate of the noise seem to match the hissing in my rear suspension air on both sides. I know the rear side has some hissing noise before you start the car from the fuel pump but is it normal to constantly be making the hissing noise? I have normal suspension, no dhp or m adaptive.
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      02-24-2019, 05:40 PM   #13
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Anyone?
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      02-24-2019, 06:25 PM   #14
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Sounds like perhaps the rear airbags are leaking and the air compressor constantly trying to add air?
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      02-24-2019, 06:59 PM   #15
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Quote:
Originally Posted by alphaod View Post
Sounds like perhaps the rear airbags are leaking and the air compressor constantly trying to add air?
Thanks for the reply. At first I thought it was air leaking from somewhere too but the car hasnt sagged at all over the 24 hour period. Tire pressure has been the same since last night, when car ignition is off no sound at all. I was told I had standard suspension so does that still mean I have airbags? I honestly don't know how my suspension is setup. Best bet would be taking it to the dealer but my warranty has ended a couple of months ago and just last month I received a good will repair for my AC/Heater issue even though warranty has expired and then they informed me that was it. Im afraid they'll make me pay for more than what needs to be fixed and knowing how gullible I am I will probably end up paying for it..
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      02-25-2019, 10:15 AM   #16
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I believe standard suspension does not have airbags. Do you have any paper work to confirm your suspension?

any local shop you trust to take a look?
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      02-25-2019, 11:07 PM   #17
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Quote:
Originally Posted by dinanF16 View Post
Quote:
Originally Posted by alphaod View Post
Sounds like perhaps the rear airbags are leaking and the air compressor constantly trying to add air?
Thanks for the reply. At first I thought it was air leaking from somewhere too but the car hasnt sagged at all over the 24 hour period. Tire pressure has been the same since last night, when car ignition is off no sound at all. I was told I had standard suspension so does that still mean I have airbags? I honestly don't know how my suspension is setup. Best bet would be taking it to the dealer but my warranty has ended a couple of months ago and just last month I received a good will repair for my AC/Heater issue even though warranty has expired and then they informed me that was it. Im afraid they'll make me pay for more than what needs to be fixed and knowing how gullible I am I will probably end up paying for it..
Do you have third row? Then you have air bags.

Easiest way is to look up under the rear. You can see the bags. Or you can see springs. Use a light.

If you have bags then it's leaking. You don't sag cuz the pump keeps it full for now. But you will soon. I had the same sound but it was from the threaded portion that goes into the bag to provide the air. It's plastic and the bolt is metal so it warps over time. Pretty sure my bags were good to go.

If you don't have bags then I got nothing lol. Could be valve stem? But hissing sound like air is very different than fuel pump sound so it shouldn't be confused for the each other
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      02-26-2019, 03:47 PM   #18
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Quote:
Originally Posted by Maverik259 View Post
Do you have third row? Then you have air bags.

Easiest way is to look up under the rear. You can see the bags. Or you can see springs. Use a light.

If you have bags then it's leaking. You don't sag cuz the pump keeps it full for now. But you will soon. I had the same sound but it was from the threaded portion that goes into the bag to provide the air. It's plastic and the bolt is metal so it warps over time. Pretty sure my bags were good to go.

If you don't have bags then I got nothing lol. Could be valve stem? But hissing sound like air is very different than fuel pump sound so it shouldn't be confused for the each other
Thanks for the reply! No sir I don't have 3rd row. I just checked after reading this and yes I see springs (atleast I know what that looks like ). I made an appointment at the dealer will check back in and let you guys know!
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      02-26-2019, 03:54 PM   #19
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Quote:
Originally Posted by dinanF16 View Post
Quote:
Originally Posted by dinanF16 View Post
Sorry to bring up a old thread but I couldnt find anything else. As of last night I've been hearing a slight hissing noise while idling at a light or slowing down to a light. It sounds like its coming from behind me on the driver side door, it's very faint but its definitely there. Im not sure if this is normal but today I looked around the car for the noise and closest duplicate of the noise seem to match the hissing in my rear suspension air on both sides. I know the rear side has some hissing noise before you start the car from the fuel pump but is it normal to constantly be making the hissing noise? I have normal suspension, no dhp or m adaptive.

Had a friend upload a video for me if this helps.
I can barely tell the noise. Maybe a tiny leak in exhaust.
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      02-26-2019, 04:19 PM   #20
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Quote:
Originally Posted by Maverik259 View Post
I can barely tell the noise. Maybe a tiny leak in exhaust.
I actually never thought about that...could possibly be considering I hear the hissing from both ends of the rear..
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      11-12-2022, 10:48 PM   #21
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Any findings on the constant hissing noise coming from the rear while engine is running? Mine is a 2010 E70 X5M. I’m having a similar constant “hissing” that I hear at idle. I thought it was my air bags, so I removed all the underbody panels to check if the compressor is running and it’s not and the hissing is persistent, and the car hasn’t sagged after being parked for over a week. The noise sounds like it’s coming from inside the gas tanks when I put my ear up to them with the under panels removed. Seems to be on both sides. Any ideas? No check engine lights.
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      11-14-2022, 09:52 AM   #22
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Dual sump fuel tanks have to have a non-motorized pump system for one side. There is fuel pumped over the to the side w/o electric fuel pump that goes through an orifice in a venturi (usually called an ejector) so that it picks up the fuel and that is delivered to the primary side with the electric pump. If there is no fuel then none is picked up. This happens the whole time the engine runs, it is not fuel level dependent. An electric pump can't be run dry so this ejector pump system is the solution. It also serves to mke a fuel reservoir for hard cornering as the primary pump is in a cup. The off side fuel(if any) is dumped into the cup. There is an ejector pump gizmo on the bottom of the cup also as keeping the cup filled until it runs over keeps the primary pump cooled and it is quieted a little bit. The fuel being sprayed through orifices in the ejectors hisses and can be heard if you're listening outside the vehicle. Noise level varies with fuel level and is usually loudest at below 1/3 gauge level as the off side is dry at that point and the off side ejector can be a bit louder then. Some versions use two electric pumps, one for delivery to engine DI pump and one only for fuel flow to ejectors. The other version has a diverted flow of fuel from main pump discharge that is the flow for the ejectors. The ones with two pumps can have a hum/whine that is barely audible since two pumps running is louder.
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