[Jamese93]

Hey Guys.

I'll ask here and apologies if this is a repeat, please humour me or send me in the right direction without too much abuse....

I've got a June 2009 build e92 325I M-sport high-line auto. Since new it has intermittently made a hissing / groaning noise that's easily heard within the car (loudest in the passenger footwell) that makes a sound for about two seconds before stopping, then starting again. It sounds to my relatively technical mind as if a pump of some description is pressurising, then de-pressurising so it has to re-pressurise again, with the hissing / groaning noise it makes as it does it.

It doesn't affect the way the car drives, is not A/C or fan related (doesn't make any difference when A/C off or ventilation completely switched off), is not related to engine speed, or auto box position. It does seem to be load sensitive, as in when there's a decent amount of acceleration it doesn't make the noise and when the car is idling you hear it.

I've never before been able to locate where the damn noise comes from (it drives me nuts inside) but today I have - it seems to comes from under the bonnet, seemingly from the pipework at the back of the engine located underneath the induction manifold to the right of the engine block.

From under the bonnet it's a hissing and groaning noise.

Any educated ideas to give the dealer a bit of direction (last time the line "we can't hear it" was given as, to be fair, it is intermittent, and they probably couldn't!)?

What is the pipework under the manifold there? Guessing fuel injection related and therefore there could be a leak in the system letting air in or out and causing a pump of some descriotion to groan?

Thanks all in advance. Want to get it sorted as it's annoying and in my mind, pumps etc don't make noises like that for too long before it escalates to constant, or just breaks outright!

J

[RichJ]

Could probably be the high pressure fuel pump?

[Jamese93]

Mmmm, did have that thought but wasn't sure where it was located. Is it under there then, any idea? Thanks for the response! J

[chris330D]

Sure it's not the power steering? Had that on my last E91 and replaced under warranty. Made the sounds you describe.

[Jamese93]

Good point Chris - but from what I recall it's electric on my car, unless the electric pumps pressurises a normal hydraulic power steering rack?

[shane55]

It could possibly be the secondary air pump...but I'm not too sure if BM use them anymore, they may well be gone out the window with the E9x series!

or

It could be the actuator motor for the fresh/recirc. air damper, which would usually be in play even if the climate ctrl. is off! I wouldnt worry about it,my car makes strange noises, one is a high pitched electrical sort of squeel which comes from under the bonnet even when off and locked!

Strange BMW computers!

[M3-FAST]

Mine does similar - I work on the theory that if everything is working OK it is prob nothing to worry about lol - it kind of sounds like it is supposed to do it if that makes sense?!

[Jamese93]

Not sure whether it's meant to do it or not - the fact it's off and on means I'm not sure about it. Ah well, at least there's a three year warranty! Thanks for the responses all J

[Jamese93]

Been into garage and it's been fixed - apparently subject to a service bulletin. It's the pipe that connects into the high pressure fuel pump - poor clips allow the pipe to touch the bodywork and the vibration from the pump then comes into the car - it will be repaired under warranty so if your car makes the noise then go get it fixed!

[ALF_E90]

This is interesting - I have just been doing a search as I have something similar - a quite loud sound that is hard to describe - perhaps a "graunching" sound is how my brain would describe it! It's been there all the time I've had the car, it is most noticeable in traffic and on short slow journeys - at speed it either doesn't happen or you can't hear it. It sounds like some kind of pump and is not related to the air con. My wife hates it - for the few times she has been in my car (we use her Golf for family duties as I put so many miles on mine) she moaned about it non-stop, and other passengers have raised their eyebrows at me! I doubt it is related to all the coil failures I've had but I'm sure it is not supposed to make such a noise!

I'll raise it at the next service, due soon - car would have been in tomorrow (this is a rare meeting-free week) for the latest misfire (assuming a 5th coil failure - only one to go!) if the dealer had managed to return any of my call on Thursday, by the time I got to someone today the slot had gone. I hate driving it on 5 cylinders but it looks like I have no choice as I have a lot of driving to do next week.

Edited to add - cancellation so car is in tomorrow - yipee! What's the betting it is coil 1 or 3 (the two originals left)... Have reported the noise also.

[m1bjr]

Driving with a misfire can seriously damage your cat(s)
Especially at motorway loads/speeds where they are likely nice and hot already.

From reading previous on this board I would also say HPFP feed pipe/ return pipe rattling.