[BMWBambi]

I have a humming/sloshing noise in the background... What is causing it? At 30 sec it can be heard best. It comes and go, like a contraction or rotation. Will try to post a video without the engine cover tomorrow for better audio.

[BMWBambi]

I guess it's hard to hear the sloshing noise. You really have to focus on it by dismissing the engine noise (including the ticking, which is normal). I wonder if it's the AC compression or ebox vent of sort. Tried taking the engine cover off but the noise it's barely recorded... It resonates more in person. My iphone XS is unable to pick it up as strongly as I hear it (hey perhaps it's me going def - ok no, not the case as the humming/sloshing stops when turning the engine off).

Anyone that is able to hear it and has any idea, welcome to comment. Cheers.

[ramparts]

has there been ice/snow on the car ?

[BMWBambi]

The car has been garaged (not-heated), in same old same London temp these days (btw -3 and 5 degrees Celsius). Haven't driven much if at all past month due to Covid. Just took it to the mechanic for oil change issue. Cheers.

[ramparts]

Originally Posted by BMWBambi

The car has been garaged (not-heated), in same old same London temp these days (btw -3 and 5 degrees Celsius). Haven't driven much if at all past month due to Covid. Just took it to the mechanic for oil change issue. Cheers.

I only ask as my wife's Mazda was making very similar noises this morning into a huge chunk of ice fell off the bottom of the car onto the road !

[chassis]

Yes, I hear it. Which engine do you have? The camera was moving around too much to see clearly.

The sound is regular. I would spend 30 minutes just listening and pinpointing the sound.

Remove the engine cover and listen. Start the 30 minute observation with a cold engine, and by the end of your 30 minute observation the engine will be warm. Please post a video when you first hear the noise at cold start, and then again another video at the end of the 30 minute observation.

Candidates:
- air con compressor, valve and refrigerant lines
- heater/coolant circuit
- intake
- EGR (which engine?)
- PCV (which engine?)
- engine mounts
- belt driven accessories or pulleys

I don't think it is these:
- timing chain
- valves
- crank or rod bearings
- fuel pump
- injectors

[BMWBambi]

Thanks for the comments thus far! Glad to know I'm not going mad - though the noise is annoying.

It's an M40i, 6 cylinder engine.

What's located next to right of the oil pan (if you were to sit on a left-hand driver seat?

Cheers.

[keithguido]

Why not ask the mechanic who did oil change?
Or better yet DRIVE it over to him?
Not sure how many owners listen under the hood of their vehicles these days.

[HighlandPete]

Besides the injection, there is the vacuum pump sound track.

I sense a sort of pulsing, (the sloshing sound?) which I'm minded won't be from the vacuum components, but could be AC or heat management induced sounds.

Does it change much with the engine cold and/or warmed up?

[BMWBambi]

Originally Posted by HighlandPete

Besides the injection, there is the vacuum pump sound track.

I sense a sort of pulsing, (the sloshing sound?) which I'm minded won't be from the vacuum components, but could be AC or heat management induced sounds.

Does it change much with the engine cold and/or warmed up?

Hmm pulsating might be a better way to describe the noise.

I drove it for about 25 minutes the other day, and made the same sound. It kicks in about 5-10 seconds after the cold start subdues. I will have to re-check and time it again though to be more precise.

I also thought that would be the case, so checked the cooling and heating inside at max and it seemed everything was working fine, inside at least. I cannot hear the noise from the inside cabin.

Anyone ever heard a *pulsating* noise in their X3? I hope it's due to something that's iced and it will fall off when I make a longer drive ha!

[HighlandPete]

The pulsing is not rhythmic, like the injection or vacuum pump, so doesn't appear to be a rotational component.

That indicates to me it involves valves, non-return valves, or flows of some kind. Vacuum pump does appear rather loud to my ear, (may be more common on the B-series engines). I'm wondering if it is something like the discharge valve, back into the crankcase ventilation system. Could explain the changing sound level and the more erratic timing of the pulsations.

[BMWBambi]

Originally Posted by HighlandPete

The pulsing is not rhythmic, like the injection or vacuum pump, so doesn't appear to be a rotational component.

That indicates to me it involves valves, non-return valves, or flows of some kind. Vacuum pump does appear rather loud to my ear, (may be more common on the B-series engines). I'm wondering if it is something like the discharge valve, back into the crankcase ventilation system. Could explain the changing sound level and the more erratic timing of the pulsations.

Thank so much for your insight! Dumb question: how essential is the discharge valve? Can it wait or best have a mechanic take a look at it asap? Thanks again!!

[HighlandPete]

Originally Posted by BMWBambi

Thank so much for your insight! Dumb question: how essential is the discharge valve? Can it wait or best have a mechanic take a look at it asap? Thanks again!!

You'd need to identify it is the problem (if it really is a problem), before looking to change parts. Cold? Possibly less sensitive in that state.

BTW, the discharge valve is essential, not exactly sure what the air balance is, but it will be part of the controlled crankcase ventilation, feeding back into the intake system. It is controlling the 'exhaust' from the vacuum pump, but can't vent to the atmosphere, as it contains oil.

There may be a way to see if it is the problem. I'd get someone to gently press the brake pedal (on and off) to use vacuum. See it it changes the frequency of the pulsating, as the vacuum pump works harder.

Does it sound the same with a few revs, change or disappear? What about when the engine is warm, or hot?

[chassis]

I just ran my wife's 30i for 5 minutes with my ear inches away from all around the engine, and heard nothing resembling the sound in the original post. To me this suggests the sound is coming from something specific to the M40i.

[Alias1431]

Kind of sounds like a belt slipping.

*This is just a thought, not backed up with actual theory. Don't even call that a guess.*

[chassis]

Location of the sound needs to be pinpointed. A mechanic's stethoscope helps with this.

[BMWBambi]

Originally Posted by HighlandPete

You'd need to identify it is the problem (if it really is a problem), before looking to change parts. Cold? Possibly less sensitive in that state.

BTW, the discharge valve is essential, not exactly sure what the air balance is, but it will be part of the controlled crankcase ventilation, feeding back into the intake system. It is controlling the 'exhaust' from the vacuum pump, but can't vent to the atmosphere, as it contains oil.

There may be a way to see if it is the problem. I'd get someone to gently press the brake pedal (on and off) to use vacuum. See it it changes the frequency of the pulsating, as the vacuum pump works harder.

Does it sound the same with a few revs, change or disappear? What about when the engine is warm, or hot?

To answer your last couple of questions, the sound remains the same when revving. Also it remains when the engine reaches optimum temp.

I will check again in a few days and try to get mechanic pinpoint the noise and will keep you posted. Thanks mate!

[chassis]

If the sound doesn't change with engine (coolant) temperature or engine rpm, it's likely not related to induction, combustion or exhaust.

Possibly air con/compressor/thermal expansion valve.

Try the test from a cold start, with air con fully turned off 100%. No fan, no "AC", temp turned all the way to the lowest setting. See if the noise appears from cold until warm engine.

Then repeat the test from a cold start with the air con at full fan, highest temperature setting and "AC" on.

[HighlandPete]

Originally Posted by chassis

If the sound doesn't change with engine (coolant) temperature or engine rpm, it's likely not related to induction, combustion or exhaust.

Possibly air con/compressor/thermal expansion valve.

Try the test from a cold start, with air con fully turned off 100%. No fan, no "AC", temp turned all the way to the lowest setting. See if the noise appears from cold until warm engine.

Then repeat the test from a cold start with the air con at full fan, highest temperature setting and "AC" on.

Agree. There has to be some AC running tests, for possible elimination.

From the OP's reply on revs and temperature, I'm less inclined to see the vacuum being involved. Although a stationary brake application test would help in putting that avenue of exploration to rest.

[TheusBimmer]

FYI you can hear ticking noise of engine. Need to bleed out the hydraulic lifter. Not sure if applicable to B58 engine.

[BMWBambi]

Cheers for that.

I will have it checked out.

I had no idea about bleeding out hydraulic lifters... not sure what they are either ha! Anyone care to explain if this applicable to our B58 engine? I'm pretty ignorant about many things. Thank you for the wisdom and information in advance!

Cheers.

[HighlandPete]

Originally Posted by BMWBambi

Cheers for that.

I will have it checked out.

I had no idea about bleeding out hydraulic lifters... not sure what they are either ha! Anyone care to explain if this applicable to our B58 engine? I'm pretty ignorant about many things. Thank you for the wisdom and information in advance!

I thought we were listening to the background sloshing/pulsating sounds. Not at any crank or 'half speed' sound track, like the obvious Direct Injection 'ticking' sound.

BTW, the odd sound is not hydraulic lifters. Besides, an HVA is a clear 'tapping' sound, it is engine rpm related (half speed), so changes with revs.