[atmosphericM]

Hey guys,

Ugh, another (hopefully small) issue has arisen on my 2013 328i w/ ~33,000 miles.

Basically, my car is making a low pitched whine that is noticeable and comes from the engine bay area. It's not the normal whine that the engine always makes. It's lower pitched than the normal whine, and I can only really notice it at lower RPMs - possibly because my performance exhaust and/or the engine noise eventually drowns it out. That said, as I rev the engine, the pitch of the sound goes up.

At first when I noticed it, I thought it might just be me, and that it was just one of the car's normal noises. But as I drive more, I'm convinced that this is a new, different noise.

Anyone familiar with these motors will know that they make a whine noise normally, it's about all I could hear inside the car until I got my performance exhaust. But this whine is different. It's more like the whine that happens when the A/C is turned on, especially right after you turn on the A/C. I have been using my A/C more often lately.. but I still only use it a few times a week and I always turn it off before I stop the engine. I baby this thing unless I'm driving hard. Even then, I baby it in ways lol. I should be clear and mention that the noise does happen when A/C is off.

It began last night. I recently had work done on the car by the local BMW dealership under CPO warranty. They replaced all 6 ignition coils, which required them to remove the cowl and engine cover, at least, from what I could tell. Not sure what else they tinkered with while in there. They also had to replace an airbag sensor, or something of the sorts, which I believe was located in the roof area. I mention that because I know that electrical issues can cause weird whines, as well, at least through the speakers. This one isn't coming through the speakers, but who knows...

Any ideas? I guess I'll have to take it in, but they charge a deductible for warranty work so I wanted to do some investigating on my own. Ugh, what a pain - I hate leaving my car with others! I'm wondering if it was somehow caused when the car was last at the dealer. It didn't start immediately afterward but it's at least a coincidence - who knows. I'm thinking maybe A/C related due to the similarity of the noises, but I couldn't tell you what that normal "A/C whine" comes from, exactly, so I don't know.

Thanks for your help!
aM

[desertman123]

You sure it's just not the natural noise of the timing chain?

[atmosphericM]

I'll try to get video footage of the noise this weekend.

In both this car and my Porsche (which has 130,000 miles), when I turn on the A/C, a distinctive low pitched whine begins. The whine's pitch follows the RPMs, and it seems like eventually (after a minute or so of the A/C 'warming up'), the noise dissipates. This is the same sound, or at least very similar. But it's happening without A/C on and does not go away. I'm just bringing up the A/C sound because if you know what I'm talking about, you'll know exactly what it sounds like. To me, it's clearly different than the normal N52 'whine,' (which you're saying is the timing chain?).

[OP3NAIR]

does it sound like electronic static (squelchy)? Unplug the exhaust flapper solenoid in the trunk and see if it stops. When you said you can’t hear it at high RPMs that might make sense. I chased this for a while and finally figured it out. With the PE you don’t need it but it will trip a soft code in the computer. Worth a try to see if that’s it.

[atmosphericM]

Thanks for the suggestion. My car does't have the exhaust flapper. I believe that's only on the 330i (and maybe some turbo models).

[Needbmwpartzz]

Are you tuned?

[atmosphericM]

Nope. Mods in the garage page. Nothing that should really affect anything like this AFAIK.

[atmosphericM]

It's hard to hear via camera. Honestly I notice it more inside the car, but when I tried to film from within the car, the mic really didn't pick it up.

If you listen closely, especially toward the end of the video, you can hear two distinct whining noises. One is higher than the other, they don't exactly follow the same pitch. I feel like the "normal whine" is higher pitched and follows the RPMs exactly. This new whine is a little lower, and it lags behind the RPMs slightly.

Thoughts?

[Needbmwpartzz]

Only things I can think of is pulleys bearings going bad...idler pulley worn(perhaps even tensioner....take off and check bearings for whine/noise)?
If noise increase with rpm.....it has to be part of rotation assembly...a/c ,belt,alternator,pulleys!

[atmosphericM]

Yeah it's got to be something that is connected to the crank. I guess I'll just have to take it in. It seems to be getting worse. Ugh =/ I was literally just there. I'll report back with what they find.

[Thorin]

Keep me posted; I have the same thing, present when the AC is on, and really is noticeable at 2000+500 RPM. I'm taking mine in this week.

[atmosphericM]

Will do. Let me know what your guy says, as well.

[atmosphericM]

Ughhh, so after over a week of this noise getting worse and worse, and being so loud and annoying that I was actually a bit embarrassed to be driving the car, OF COURSE this morning.. the morning of my appointment with the BMW dealership.. the noise is gone. Well, I say gone, but I think it's just back to it's "appropriate level." So now I look like an idiot, but I'm not crazy lol, I swear!

After talking to the actual mechanic/tech for a minute, I think the noise is the alternator. I could still hear it today, but it was very faint (so quiet that I would never really notice or point it out), and when I pointed it out the guy said that's the alternator (makes sense). But of course, it was so quiet that there was nothing that could be done. So now I have to wait for it to (hopefully) come back (before warranty expires) so that I can take it in. This is what I get for making an actual appointment instead of just driving straight there like I usually do when something goes wrong, lol.

Does anyone know if ambient temps can affect alternator noise? The only reason I can think of as to why it's so quiet today is because it's, relatively, very cool today. Typically it would be 85+ degrees outside by 8 am, but because it's cloudy and misty, we're rocking a chilly 75 outside. That is quite rare for here. Perhaps that's why it's so quiet today?

Also, though, he checked the power steering reservoir as that's obviously another potential culprit. He said the fluid level was very low. I just bought this car, CPO, from the same dealer a year ago almost exactly. Actually right after I got it, I noticed that there was gunk around the cap, even though the rest of the engine bay was pretty dang clean. I thought it odd but didn't think too much of it. Not sure how or why that level would be low. Car only has 32k on it, too. Perhaps the PS fluid was low and that was causing the noise? But still, why would it have been so quiet today? And I doubt that the fluid all of the sudden dumped out - this whine noise started abruptly for the most part. Grr.

[e90yyc]

This is only in relation to your PS question, but the reservoir caps are notorious for leaking.

Mine used to leak quite a bit. Not sure it was necessarily hemorrhaging fluid, but enough that it was always wet and therefore a dirt magnet.

Replaced reservoir and problem is gone.

You could probably just knuckle the cap on really tight, but honestly, for the cost of replacing the reservoir (and by extension, the built-in filter), I'd just do that.

You can also get cap separately.

[atmosphericM]

Hmm car is under warranty so I might try to get them to replace the reservoir. CPO car with warranty and such low miles, sold for a premium obviously lol, shouldn't have a leaky dirty PS reservoir in my book.

[e90yyc]

Agreed. I'd think they should replace it.

I'd be a bit surprised if your low fluid was due to a leaky cap though...? Definitely worth a mention to them! Take full advantage of that CPO, as I'm sure you are! :-)

[d1saster]

Is your AC properly charged with refrigerant?

[Thorin]

Originally Posted by d1saster

Is your AC properly charged with refrigerant?

This is what mine was. The shop changed the Schrader valves, checked for leaks, and topped off the refrigerant. Another data point was my AC blew cool, but did not blow ice cold, so that was a tell.

[calicolorado]

That sounds exactly like my alternator when it was just about dead. Mine went at about 150K, but I suppose they can fail prematurely. I thought that I killed mine early by occasionally pressure washing my engine, but I figured that 150K was decent service life out of the part. I'd bet that's exactly what's wrong with your car.

[atmosphericM]

Originally Posted by d1saster

Is your AC properly charged with refrigerant?

I assume so. A/C in this car is definitely not amazing though, IMO. Car is only a year old since sold as "CPO New," though obviously you can't trust most, these days.

[atmosphericM]

Originally Posted by calicolorado

That sounds exactly like my alternator when it was just about dead. Mine went at about 150K, but I suppose they can fail prematurely. I thought that I killed mine early by occasionally pressure washing my engine, but I figured that 150K was decent service life out of the part. I'd bet that's exactly what's wrong with your car.

Yes sir we have a winner!

Not wanting to be defeated, I drove the car more than I usually do, yesterday. At one point, I heard the noise for a moment as I was getting on the highway. By the time I got off, and could try to hear the noise, it was gone again. Ran a few more errands and luckily it finally appeared as I started my car after the last errand! I drove it straight to the dealer, which luckily was still open.

The tech did a quick diagnosis with his stethoscope and concluded that it's either the alternator itself, or the bearing attached to it. Will report back with a full diagnosis once I get the car back.

Rocking a new X3 in the time being.

[e90yyc]

Right on! But at 33k miles? Damn.

Alternator bearing is not replaceable separately, right? I know the pulley itself is, but have never seen a PN for the bearing inside.

Glad you found the source of the noise!