3.0L M54 engine whirring noise

[rmr2122]

I recently finished a major engine service project on my 2006 E53 with 90k miles on a 3.0L M54 engine (oil filter housing gasket, coolant overhaul including pipes under intake and all hoses, DISA rebuild using GAS kit, installed GAS ccv kit and removed stock ccv, lower intake boot, cleaned throttle body and replaced gasket, cleaned idle control valve, idle control valve grommet, removed intake and replaced gasket, replaced tensioners, idler pulley, spark plugs, VANOS seals, valve cover gasket). It was a big project!

My engine is running like new! I loved this project and am excited to do it all again on a friend’s e53 in a couple months.

I’m attaching a video of my engine below and wanted to get your feedback on the high pitched whirring noise. It gets higher pitched but not louder when RPMs increase. I’ve watched a bunch of M54 videos on YouTube and I definitely hear this noise on other peoples engines, but I can’t decide if it’s a problem or not. Can you take a listen and let me know if this whirring noise is within normal bounds?

https://youtube.com/shorts/sBBemGyJ3_Q?feature=share

Thanks!

[80stech]

That sounds like an alternator with a misaligned field.

[rmr2122]

Is that something I can fix? Or do I need a new alternator? How long can I drive with a misaligned field?

[80stech]

It's just a noise thing so you could drive it as long as you are ok with the noise, if not then you could replace the alternator or have it rebuilt (better choice) at a shop that does that sort of thing. I think there is one model of alternator used on the X5 that is particularly sensitive to this, rough handling/shipping or accident can cause it to get knocked out of alignment.

[rmr2122]

I did power wash the engine pretty aggressively during the maintenance! The alternator was completely coated in oil and grime so I couldn’t resist cleaning it up. I wonder if I could’ve misaligned during power washing or even removing/reinstalling for the oil filter housing gasket.

[oldskewel]

Originally Posted by rmr2122

I did power wash the engine pretty aggressively during the maintenance! The alternator was completely coated in oil and grime so I couldn’t resist cleaning it up. I wonder if I could’ve misaligned during power washing or even removing/reinstalling for the oil filter housing gasket.

I power wash my alternators every chance I get. ( but not completely kidding) I definitely wash oil off them when I can. And yes, I've been reading what the intertubes say about this for decades now . I try to do it when the engine is warm so any residual water dries off quickly. Any sensitive electrical components are generally well sealed, and anything that is not sealed is generally very durable and resistant to water. Yes, I'll agree that if everything is kept perfectly dry, that should be OK too.

I rebuilt my Valeo 120A alternator when the slip rings wore out, also replacing the bearings since they had to come out anyway. Here they are, NTN 6303LU front bearing and NSK 6202DU rear bearing. Both have contact seals, and both were working just fine when removed at around 170k miles. These cars alternatively came with Bosch alternators - I don't know details on those.



From my experiences with my own old cars, I believe the thing that kills alternators other than normal wear and tear, is when they get wet with oil (or PSF, etc.). They are designed so the soft carbon brushes eventually wear away, hopefully after 150-200k+ miles. The powder debris from the wear escapes from the brush assembly through carefully designed ports. It has to go somewhere.

When oil (that won't evaporate, as water will) gets in there, the powder debris does not dissipate as it should, it collects and forms an abrasive paste that is always there, and accelerates wear on the slip rings, leading to alternator failure. Slip ring replacement is at least 10x tougher than any other alternator repair, so failure of that component usually means the alternator is dead.


Also - don't read all this talk about alternators to mean I think you have a bad alternator based on your video. You might. Tough to tell. It definitely does not sound right. Well done on getting all that work done. I'd spend some time with the diagnosis. Good luck.

[wpoll]

I foresee alternator bearing replacements in your near-future!

[rmr2122]

Should I replace the entire alternator with a unit from FCP? Or better to keep my OEM and just replace the bearings

[wpoll]

Originally Posted by rmr2122

Should I replace the entire alternator with a unit from FCP? Or better to keep my OEM and just replace the bearings

First confirm it IS the alternator bearings, although power washing the alternator is bound to be the cause of this. Alternators need to stay dry. I always put a grocery bag over mine if I'm washing down an engine bay.

Remove the belt and run the engine (for a SHORT time!) - if the noise goes away, it's something the belt is spinning; an idler, a tensioner, the water pump or the alternator.

You can also use a long rod or large screwdriver as a "stethoscope", placing one end on the alternator housing, tensioner etc. and the other end against your ear, to listen for the source of the noise.

It's without a doubt it some that rotates!

[rmr2122]

Also can I drive the car until I get around to replacing the bearings? Or will they likely seize on me shortly?