Just wondered if anybody could help me with this, I turned on the ignition on my 2002 Z3 3L and could hear what sounds like a fan running. (Engine not running) Trying to locate the fan noise, it sounds like it is coming from the OS fuse and relay box at the rear of the engine bay. I hope I am not showing my ignorance of BMW cars or posting in the wrong place. Any help welcome. Thank you
Sounds like a fan running
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There is a buzzy sound under the hood/bonnet of all 6 cylinder Z3's when you turn the key on. It comes from the Idle Control Valve (ICV) and is normal. Nothing to worry about.
Always wondered what that buzzing was... but that sound is more from the centre of the engine?
The noise from OP is coming from the fuse box area. Does an M54 in a Z3 have an additional water pump? Had to look up what that was as I can't remember seeing or hearing of one before. As it's coming from around the fuse box I initially thought you meant the water valve.
Its not a noisy smog pump is it O/S front behind the headlight these run at ignition and are known to go bad an become noisy ?.
The Secondary Air Pump (SAP) only turns on for around 30 seconds when the cold engine first starts, not with just the ignition turned on.
The OS box at the rear of the engine bay houses the ECU and various other box of tricks, there is a vent tube which routes down from the housing in to the car just above the pedal box, any noise coming from this box will be amplified to some extent in the cabin area.
I have stripped the ECU housing (for want of a better description) but cannot remember if there are cooling fans in there.
I have stripped the ECU housing (for want of a better description) but cannot remember if there are cooling fans in there.
There's no fan in there but it does have cooling ducts bringing in cold air.
However the OP talks about the fuse/relay box which is on the other side. OS may mean outside or may be confusion between O/S & N/S ??
Hi All, Thank you very much for taking the time to reply. I have read all the reply's. Sorry about confusion with OS I mean Off Side (not Kerb Side). Turning the heater to cold made no difference. I have now taken the cover of the fuse and ECU box and the fan noise really seems to be coming from here and when I touch the ECU I can feel slight vibration and the tone chances slight. I feel that @Brian H could be on the right track and perhaps one of the ECU's may have a cooling fan which then vents through the rear vent tube.
I have a quick video which you can see and hear the noise, not sure if it helps or not
https://www.dropbox.com/s/i9tz6qw8monm7jb/Fuse Box Fan Noise.mp4?dl=0
Thank you for your help
I have a quick video which you can see and hear the noise, not sure if it helps or not
https://www.dropbox.com/s/i9tz6qw8monm7jb/Fuse Box Fan Noise.mp4?dl=0
Thank you for your help
There's no fan in the enclosure. And no fan in the ECU (DME) case itself. Not unless your build is anything different to what I've ever seen before.
However if your ECU is making the noises, and I don't see why it would as it's solid state, and if it did it wouldn't be a fan noise, you don't want that going kapput while you're driving.
There's nothing else in that enclosure that would make a noise like a fan as it's all dumb wiring and relays. Unless I suppose the air stream through the cooling ducts is very rapid and a leaf has got caught up in there and is rustling. I doubt either.
Most likely to be coming from something nearby I would think. But I'm intrigued and happy to be proved wrong.
Here's a pic inside the enclosure (DME removed).
I just listened to the recording. It doesn't sound like a fan to me. Well it's very unlikely to be anyway as there aren't any fans in that corner.
It's more of a mechanical hum. If I had that noise I think it would trouble me deeply. I don't like it. That doesn't mean it's something bad but I would want to know.
I think you need to be certain of where it's coming from. If it really is the DME that's weird and will need attention. It's a solid state box of tricks that sits in a passive environment. In an area of the engine bay where there isn't really a lot going on apart from the brake servo and if fitted (and it's at the front not back) the Secondary Air System (big vessel by the front panel). Most Z3s don't have this. Not sure I've ever seen a 3.0 with it. I hope it's not the DME as that is not cheap or easy to replace. 2 min job to switch but needs programming for your car.
My best guess is it's a referred sound coming from elsewhere but seems like it's the DME.
It's more of a mechanical hum. If I had that noise I think it would trouble me deeply. I don't like it. That doesn't mean it's something bad but I would want to know.
I think you need to be certain of where it's coming from. If it really is the DME that's weird and will need attention. It's a solid state box of tricks that sits in a passive environment. In an area of the engine bay where there isn't really a lot going on apart from the brake servo and if fitted (and it's at the front not back) the Secondary Air System (big vessel by the front panel). Most Z3s don't have this. Not sure I've ever seen a 3.0 with it. I hope it's not the DME as that is not cheap or easy to replace. 2 min job to switch but needs programming for your car.
My best guess is it's a referred sound coming from elsewhere but seems like it's the DME.
Pull each relay in turn to see if the noise stops. A relay can make that sort of noise when its on the way out. Note where they go as each relay is colour coded and different.
A bit of digging in the electrical trouble shooting manuals and I found this, the Z3 is wired for a E-Box Fan!
I suspect this is for warmer climates, normally it would be worth pulling Fuse 26 to see if the noise stops but Fuse 26 also manages the following: -
I suspect this is for warmer climates, normally it would be worth pulling Fuse 26 to see if the noise stops but Fuse 26 also manages the following: -
Well done! There is at least 1 spare connector in there, probably 2 I think as there is 1 for the SAS from memory.A bit of digging in the electrical trouble shooting manuals and I found this, the Z3 is wired for a E-Box Fan!
I suspect this is for warmer climates, normally it would be worth pulling Fuse 26 to see if the noise stops but Fuse 26 also manages the following: -
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I get the same on my M when the ignition is turned on sounds like a fan running above the pedal box ??
Does it make the same sound as in the video though? That’s not really a fan noise. If it really is coming from the DME enclosure then I feel it must be a bad relay. But it might still be a referred noise from somewhere close by.
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Nope sounds like a fan and I swear I can feel air blowing
The ///M definitely has a fan.
Hi All. That is a really great result, @Brian H you must have spent some time digging that out for me, well done and thank you.
I spent a bit more time hovering over the area with the cover removed and I can also feel a draft of air when the fan noise is present.
I think that the noise in the video is not really a good reproduction of the actual noise, Maybe if @mrscalex actually heard the real noise he might say, yes it sounds like a fan (or maybe not).
Anyway I am now happy believing that it is a fan and its all as it should be. Thank you all for helping me.
I spent a bit more time hovering over the area with the cover removed and I can also feel a draft of air when the fan noise is present.
I think that the noise in the video is not really a good reproduction of the actual noise, Maybe if @mrscalex actually heard the real noise he might say, yes it sounds like a fan (or maybe not).
Anyway I am now happy believing that it is a fan and its all as it should be. Thank you all for helping me.