[Neosakai]

I've searched all over and watched a bunch of youtube videos but can't seem to find someone with this exact noise that I'm dealing with

My 328i xdrive drove fine up until yesterday I started hearing this very strange noise coming from the engine bay when the car is cold. Once the car is warm enough for me to start driving, I hear this grinding? howling? gurgling? noise when I accelerate very lightly from a stop until 20km/hr (12 miles/hr) then the noise goes away. The car drives fine but the noise is very noticiable.

I took the car to my mechanic today and we couldn't figure out what it could be. The noise isn't rotational, has nothing to do with belts/pullies (we tried taking out the belt and still hear the sound when taking off. There is no noise when reving it in neutral/park either.


Tried my best to take videos of the noise.
In the first video you can see that after 20km/hr the noise goes away

In this video you can hear it from the engine bay during cold start, during 0:05-0:09 its pretty noticable

Some info about the car:

I purchased my 2011 328i xdrive two weeks ago at 164 000km (101 000 miles). I 've done the following since:

oil change - liqui moly 5w-30, Mahle filter
brake fluid
power steering fluid
transmission fluid - filter + seal
checked coolant and done the bleeding procedure multiple times

My mechanic did go back and check all the things listed above that was done and nothing seems off


Any help is appreciated!

[Neosakai]

Heres what it sounds like from the engine bay on a cold start (its hard to hear from the engine bay once it warms up, but can definitely hear it inside the car when accelerating from a stop)

Its hard to describe the sound but its like water gurgling down the drain or something.

[wafflecougar]

Originally Posted by Neosakai

Heres what it sounds like from the engine bay on a cold start (its hard to hear from the engine bay once it warms up, but can definitely hear it inside the car when accelerating from a stop)

Its hard to describe the sound but its like water gurgling down the drain or something.

Have you tried scanning for codes? I'm not sure what the sound could be but if there are any codes that might help. Good luck.

[Neosakai]

Yeah no codes and the car seems to drive fine so I have no idea what the sound can be and its been driving me nuts

[sav_e92]

So, I recently installed a Euro airbox and intake resonator delete (silicone hose), and for fun and a little extra noise I've left the cover off the airbox. Since installing all of this a few days ago I've noticed a similar sound in similar conditions (cold start, slow speed, very little throttle).... but I haven't paid much mind to it since my car seems to drive fine and the sound goes away. It has also been brutally cold in my area (Northern Vermont), like 5-10 degrees F and I've wondered if that correlates.

If I have a chance tomorrow I'll put the cover back on my airbox and see if the sound persists. Have you done anything to your intake path recently, or checked it? I'm wondering if maybe we're both experiencing a leak of some sort, in my case, probably due to me running with no airbox cover... and maybe that sound is some intake air bouncing around somewhere it doesn't normally go? Just a thought.

[Neosakai]

Originally Posted by SAVAGE_VT_E92

So, I recently installed a Euro airbox and intake resonator delete (silicone hose), and for fun and a little extra noise I've left the cover off the airbox. Since installing all of this a few days ago I've noticed a similar sound in similar conditions (cold start, slow speed, very little throttle).... but I haven't paid much mind to it since my car seems to drive fine and the sound goes away. It has also been brutally cold in my area (Northern Vermont), like 5-10 degrees F and I've wondered if that correlates.

If I have a chance tomorrow I'll put the cover back on my airbox and see if the sound persists. Have you done anything to your intake path recently, or checked it? I'm wondering if maybe we're both experiencing a leak of some sort, in my case, probably due to me running with no airbox cover... and maybe that sound is some intake air bouncing around somewhere it doesn't normally go? Just a thought.

Ive actually changed my air filter (im on stock airbox, just using mann filter) recently so at first I thought it might have something to do with that. But Ive taken it back out and carefully reinstalled my airbox but the sound is still there... Perhaps I should maybe try starting the car without my airbox (not sure if this is a good idea) to see if the sound is related.

[sav_e92]

Originally Posted by Neosakai

Ive actually changed my air filter (im on stock airbox, just using mann filter) recently so at first I thought it might have something to do with that. But Ive taken it back out and carefully reinstalled my airbox but the sound is still there... Perhaps I should maybe try starting the car without my airbox (not sure if this is a good idea) to see if the sound is related.

Yeah probably don't start w/o the airbox at all... you'll want the MAF sensor to be measuring the air heading into the engine at the very least.

I did put the cover back on my euro box today and I didn't hear the gurgling sound... I did also notice that my blower motor may be starting to fail as I can hear it squeal a bit on sharp turns... don't know whether that could be related but since the noise is oscillating in nature I thought perhaps the two could connect somehow.

[Neosakai]

Originally Posted by SAVAGE_VT_E92

Yeah probably don't start w/o the airbox at all... you'll want the MAF sensor to be measuring the air heading into the engine at the very least.

I did put the cover back on my euro box today and I didn't hear the gurgling sound... I did also notice that my blower motor may be starting to fail as I can hear it squeal a bit on sharp turns... don't know whether that could be related but since the noise is oscillating in nature I thought perhaps the two could connect somehow.

I guess I'll take off my airbox one more time and maybe inspect the tubing for any cracks. Its extra frustrating since im 100% stock

[Neosakai]

So I took off my airbox once again and checked all the tubing for any cracks and what not. Everything seems fine so I'm completely lost at what could be causing this