High Pitch Sound

The fault is almost certainly an alternator bearing or pulley wheel. The alternator is making a whining noise when I listen to it with a stethoscope. The only thing making me unsure, is that the noise through the stethoscope is not that similar to the noise you can hear in the video, but god only knows how the noise from within manifests itself audibly when it occurs. Everything else is purring along nicely, except the HVA noise, but I can and have lived with that for ages.

My issue now is having the time (as the car is my daily runner), to strip the alternator, which is packed in like Linford Christies gentlemen parts, in his running shorts, and establish for sure that it is the bearings before swapping them out.

Rock and a hard place, I'm afraid. :headbang: Will post pictures of the strip down and rebuild, as there doesn't appear to be anything on the web about this job. Think most people must just swap the alternator out completely.
 
So I stripped the alternator today. All is absolutely fine! Now I should be happy, but, it leaves me with absolutely no idea what is wrong and the same problem.....

My only other idea is, that something has got lodged in the oil housing, oil lines, in the cylinder head, or in the sump, and is acting as some sort of membrane, that is creating the whining noise under pressure. Kind of like a kazoo type effect. This would explain the noise being the same as when I replaced the filter housing last year.

My only port of call is to drain the oil, flush it and hope that something comes out, but I don't hold much hope, as I think the guilty item, will be lodged somewhere, hence the whistling, whining noise.

Can anyone advise wether the oil drain should take anything in the system with it when drained?

I'm at a complete loss now.
 
MHZ4C said:
Hi GedS, any luck with the alternator?

I have an intermittent whine on mine (N52). Only when the engine is hot. It's hard to tell but think it is similar in pitch to your noise. It's engine Rev related too.

I had a new alternator, serpentine belt & pulleys from BMW under warranty. Initially the noise was quieter, but is still present.

The tone doesn't change when stationary in neutral, or with clutch peddle up or down.

I'm doing so few miles that it's hard to tell if it is getting worse or not. It's not that noticeable when in the car, so I've not looked into it since the alternator, belt & pulleys were replaced over a year ago.

I read that you can test the waterpump while the engine is turned off, to confirm if it's the pump or not. Something to do with holding the accelerator peddle down with the ignition in position 1.

Other than that then there're a few other things on the serpentine belt as well as the alternator; a dampener wheel & the aircon compressor pump I think. The idea of running briefly with the belt off is a good one & would take anything to do with the clutch & flywheel out of the equation.

Fingers crossed you get it sorted with minimal cost mate. I'm interested to hear how you get on, or if I can offer any help with noises from another N52.
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Your issue sounds like a dodgy oil filter. When did you last change it? Check it's not crushed and if you do replace it, use only the Mann filters. There have been issues with the ones garages have been using.
 
Hi,
Did you try running the engine with the belt off, the sound on the vid really sounds like a bearing squeal - If not alternator then maybe one of the tensioners.
Stu.
 
Have you tried the electric waterpump? Maybe you can start that with a seperate power supply.

The n52 also has a seperate vacuum pump (because valvetronic). Maybe that can be a cause?
I'm not 100% familiar with the n52 like with m54 or s54, but I think that might be quite a job to replace.
I'd go investigating some more with an engine stethoscope. A sound that loud should be easy enough to find. Be careful not to damage your ears; I have an engine stethoscope too, and it is really loud, especially the plop when you put it on an engine part (or accidentally move it).
So I always first place the top firmly on the part of the engine I want to listen too, and only then put the plugs on my ears.

If the engine was direct injection, I'd suggest maybe listening to the injectors. But maybe the pulsating frequency is a bit too high for that.
If your alternator was whining, it was also bad, although not the cause of that 'nasal' ratteling sound.
I cant imagine it being caused by something in the oil system. In the oil filter housing there probably is a check valve, you know to keep pressure on startup etc like the m54 has; but as I said I dont know the n52 so well so maybe some of the 3.0si owners can verify that.
That might flutter? maybe with alternating pressure? That's the only thing I can imagine to make noise in the filter housing if you're looking for a cause in that direction
 
Hi GedS

Yes, I was reading about the filter issues on other N52 engines on the 3 series:
http://www.e90post.com/forums/showthread.php?t=681808
The noise from mine is quieter and changes pitch with engine revs. So not identical, but I'll unscrew the filter housing and take a look. Easy to check.
I changed the oil filter & oil 7K miles ago. I can't remember if I had the sound before that; it was over 1.5 years ago, so due another oil & filter change anyway. The filter was OEM from BMW so no guarantees that it was ok!

Sorry to hear you still have the sound. At least your alternator is fine. I'll see if I can find any info on the oil route from the filter housing.
 
Purely on a time factor (as this is my everyday runner), I have had to accept defeat, and book it in at the garage. The garage has worked on my car before, and despite being expensive IMO, they are very good, and I trust them.

I have asked them to give me a full report on the diagnosis of the problem, and the process of elimination they go through. It is booked in for Monday, so fingers crossed that its something and nothing, i.e. a bearing, split hose........God knows, but not too serious!

The car drives absolutely perfect, except for the f**king noise, so I'm optimistic. Updates to follow.....

Thanks for all your help and efforts guys. Much appreciated. Hopefully the rest of my time can be spent on upgrading & modding, not fixing.
 
I had a read about the deformed filters.

There's good advice above about trusting Mann filters.

I changed my oil filter, but I can't remember if I had the noise before or after the filter change.
This post opened an idea:
http://www.e90post.com/forums/showthread.php?t=835145

I didn't realise that the filter clipped into the filter housing lid. So a brand new filter can go in, not be clipped in, then deform as the lid is tightened down. I can't remember if I clipped the filter to the lid or not.

When I get some time I'll take the lid off of the filter housing and check the filter for damage.

I see you've investigated the filter housing and had a new oil filter. My question is; did you clip the new filter into the filter housing? If not, then it's worth a 2 minute check removing the filter housing, even though it was a new filter, as the failure mode for old and new filter could be the same, even with a good Mann filter, as it would still be twisted as the housing lid was torqued down to 25 NM.

Apologies if you're already aware of this. I wasn't, so thought I'd put it out there at the risk of showing my limited knowledge! If you've confirmed this then I'd really appreciate hearing the garage diagnostic report. Fingers crossed for you having a cheap fix!
 
Ok, a quick update.......

I decided to have one last look at this noise issue. The reason for doing so, other than my pride and joy making a racket, was what appears to be the most fortunate bit of inspiration I've ever had.

Started work at 4pm today, and was watching a bit of tv and browsing the web, and I saw a video on Facebook of all places, of a lad on his bike in the early 90s with a plastic bottle in the rear wheel to make it sound motorised.

You can probably see where this is going......,

I recognised the noise to be very similar to what I was experiencing. Soooooo off with the front of my z4 coupe!!

Low and behold, the belt that drives the alternator etc was rubbing on a cover on the bottom wheel near the tensioner pulley. It would appear, that the belt has somehow shifted over by one rib on said wheel. I re seated the belt and added some white grease to all the bearings/moving parts and hey presto!!!!!! I have no idea why it was was like this, but when I loosened it off to check the alternator, I didn't check the other wheels only the one on the alternator where the main noise "appeared to be", nonetheless, sorted now.

No more noise!!!!!!!! :thumbsup: one very happy owner, of a very quiet BMW Z4!!

True story! :D
 
Well done! Congratulations on finding such a simple resolution. Saves a trip to the mech and one to add to the list of noises.
 
Nice one!

Can you give a bit more advice on what you greased Please? I reckon whatever it was will benefit my noise too!
 
-Green arrows = Areas I sprayed the white penetrating grease in either side of the wheels, bearings
-Red Arrow = The offending cover rubbing the belt
-Yellow Arrow = The belt that had moved slightly, touching the cover (red arrow)
***The black cap on the alternator pulley wheel, I removed and sprayed inside***

There was very little scientific, or measured spraying, if it spins, spray it!!
I am not great with car part names or terminology, but I am very good with tools and used to work a lot on push bikes, and all the faults I have come across so far, I have fixed very similar issues on bikes. Bearings (if not deformed or worn) react very well to white grease, and lots of it. That is all I did, other than re seating the belt.

The main noise was from the pulley wheel on the far left, above the red arrow.

The more I think about it, in the summer last year, I had the engine steam cleaned. I wonder if this removed some essential lubricants.....

 
Great that you've stopped the noise! Did you remove the bumper for access?

It's odd that the belt was off slightly. The only thing I can think of is that maybe the tensioner is worn slightly, so allows the belt to wander enough to slip by a rib.

In any case, keep an eye on the belt sitting tight, enjoy the engine running without that noise, and congratulate yourself on a job well done, without paying anyone!
 
enzed4 said:
Brilliant you found this at the 11th hour :thumbsup: Well done, now get back to enjoying the Z4 :D
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Forgot just how nice it is to drive this car, without it sounding like its about to explode! I am definitely smitten all over again!
 
MHZ4C said:
Great that you've stopped the noise! Did you remove the bumper for access?

It's odd that the belt was off slightly. The only thing I can think of is that maybe the tensioner is worn slightly, so allows the belt to wander enough to slip by a rib.

In any case, keep an eye on the belt sitting tight, enjoy the engine running without that noise, and congratulate yourself on a job well done, without paying anyone!
Click to expand...

I removed the radiator originally, which was unnecessarily difficult to do, but if you don't have access to a ramp, is the only way. The offending parts are easy to reach from underneath, by removing the bash plate and the trim that attaches to the front bumper. You are staring straight at the parts from there.
 
Would appear that the fix was only temporary, as the noise is back. At least I know the origin of the noise, and hopefully a new belt should solve the problem.
 
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