Whining noise from beneath car...

BMWZ4MC

BMWZ4MC

Lifer!
 Diving out of the sun
Hi guys, I wondered if anyone has any ideas what might be causing this:

Several weeks ago my car developed an unusual whining noise that seems to come from beneath the car. It seems not to be present when the car is cold, but is very prominent once warm. It is there when moving or stationary, and is not dependent on clutch position or whether or not the car is in gear. Interestingly, it is at least as loud from within the car as when standing next to it. It seems to emanate from the centre of the car, not from the engine compartment (unless engine noise is drowning it out when I listen there). There is a slight warble to the sound as if something is precessing whilst spinning.

I've experienced a very high-pitched whistle from the fuel pump on previous cars, especially on very hot days, but this seems a lower-pitched whine, and is present even on cold mornings.

The only other (perhaps unrelated) symptoms are an occasional misfire and an intermittent flat spot in the rev range at around 3,000 rpm when bumbling along in third gear traffic. I have experienced also one episode where it started and ran extremely roughly and hunted at idle with the emissions light illuminated. This settled on restart, and the warning light went out after three subsequent normal restarts. Since then, the car has driven normally save for the whine. I should add that the whine pre-dated the rough running by several weeks, so these may represent two separate issues.

I've checked for logged OBD II codes, and found only P1417 which is a port air relief circuit malfunction, or perhaps just a phantom code (thanks mmm-five in your Pistonheads guise!).

Finally, the car is a 38,000 mile 56 plate ///M coupe, which has about 8500 miles to go before Inspection II.

I've had a look underneath the car, and I've not run over my neighbour's mother in law (I don't have one of my own), so any thoughts and advice about the source of the whining would be most gratefully received :D

Cheers, Richard
 
Sorry, I have no idea on the noise you've got but I'm interested about your comment regarding the high-pitched whistle noise. Just lately I've had this whistle noise, which appears to come from (and I can only go by my experience while driving it) underneath or the rear part of the car.
If I hold at a constant steady speed, it doesn't happen, but when I accelerate even slightly it occurs. Is this most likely to be the fuel pump then? If so, does it mean it's on its way out?


Neil
 
Hi Neil.
Without hearing it, I don't know if your sound is the fuel pump either!
The fuel pump noise I've experienced previously has been a characteristic whistling noise of constant pitch. Usually this would occur on especially hot days or after a spirited drive. I've heard it from several cars (but never from a car with carburettors), and have never had a fuel pump problem, so I think it is normal.
Whether your sound is this, I don't know - the fuel pump sound I've heard has not obviously been related to engine speed / road speed, and certainly was present at idle.
Hopefully someone else will be along soon to help us both out! :D
 
Might be worth getting the fuel pump checked out. On my old (non M) Z4 Coupe, the fuel pump would whine - and get louder when warm. Turned out to be a faulty pump on its way out and was fixed under warranty. Car went better too as the pump wasnt delivering enough pressure under full load.

James
 
shambolic said:
Did you run over the Missus?
:D
Click to expand...
Since non-serious replies seem to be on the cards, I'll suggest checking under the car for the England football media...




:poke:


:wink:
 
James coupesport - thanks for your help. Hope it isn't the fuel pump as I'm warrranty expired, but that might explain my other intermittent running issues when in traffic. That said, mine still pulls like a train up to the red line so it certainly works under duress. Did you notice if the sound ever changed pitch or any other characteristics?

Everybody else - thanks :D
 
as has been said there have been a few fuel pumps failing. easy way to make sure it's the pump is does it get noticably quieter when the tank is full to the brim as opposed to nearly empty?. that would eliminate all other culprits. and with such a high compression engine it would be best to get it looked at sooner than later as running lean isn't even worth thinking about
 
...... do Zeds have an inline fuel filter ???????

just throwing that into the mix, I had one blocked on another car once restricting flow and overloading the fuel pump. :D
 
BMWZ4MC said:
Everybody else - thanks :D
Click to expand...
Ah well, I couldn't contrbute constructively to your problem solution so I thought trying for a laugh was the next best thing :D
 
The whine was constant in pitch but varied in volume. We were looking at houses at the time so spent a lot of time in the car stuck in traffic and the noise would get louder as the fuel warmed up. It was quite noticeable in the car too as the sound appeared to come from behind the rear bulkhead and as Gorbash says it got louder when the tank was near empty. It was a days job - drain the tank, drop the tank, remove and refit pump - hope whatever it turns out to be you get it sorted.

Cheers

James
 
Gorbash12346 and Coupe-sport, it certainly sounds like you're describing the same problem.

Interestingly, the sound seemed to be absent the last few times I drove the car. I've gone from a brim-full tank to now running with the the fuel warning light illuminated, but still nothing... I'll see what happens when I get to drive it more over the weekend.

Again, thanks everyone for your suggestions.
 
My whistle is not an 'air-like whistle' sound like a turbo makes.
There is no change in pitch, it is one constant sound and it sounds almost like a mechanical thing that is causing it, not air rushing into or out of something.
It does it in any gear and regardless of how much is in the tank.
But it doesn't do it in neutral, whether stationary or moving.
It does it from cold engine through to hot.
There is no change in performance at all, I can rev right up and it pulls perfectly.
The car is a 2.5 Z4 Sport, by the way (bought from a regular contributor to this very forum (who therefore clearly looked after it)).
What triggers it is pressing the accelerator. Not holding it steady like when you're sticking at 50 or whatever. But if the limit changes from 40 to 50 and you just push hard enough to reach 50 driving, you know - sensibly, then that'll do it, all the way up to booting it hard. The very slightest touch doesn't quite make it happen though.
Sounds like it's coming from the left side of the car and towards the rear.
If anyone can work it out from that who isn't in the engine diagnostics business, you should be.

Neil
 
Well today I found out what the noise was (it seems like I'm writing a reply to myself here) and it's a split hose. Apparently it's connected to the hot film air mass meter - see picture. Tried looking for this part online but only US sites seem to sell it. Can't be hard to get one and it's only a few hose clamps to undo to fit one. Does anyone know a good site selling BMW parts - one that doesn't just sell car mats and silvery trinkets?

thebit.jpg
 
What took so long was me being a slacker and focussing on the more serious problem of a dying brake caliper (now sorted). I asked the mechanic (my cousin) to check for the whistly sound and he lifted the bonnet and found it straight away. I took the advice about going to Sopers BMW and they've confirmed the part I need and I'll be ordering it tomorrow. Thanks for that.
I even reckon it's a bit I can fit myself (and it's only £16).

Why am I still listed as a newbie? How long does that take to go away?

MYZ.jpg
 
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