SOLVED!: E53 X5 3.0 sounds like dying banshee on fire when I take my foot of the gas

[oldskewel]

Bearings can make sounds like that, that come and go very abruptly. The instant on / off is an important clue here. Foot off the gas would let the engine spin down, changing the drive belt tension, which might trigger an alignment shift in a worn, dry bearing, that might turn the sound on instantly.

Is there any way you can recreate the sound while it is parked? If not, that's an important clue too. And it will be tougher to diagnose.

Sounds in general can be really tough to trace. Has the problem progressed to the point where it is exactly predictable when it will occur, and if so, what is the easiest way to get it into that state? For example, easiest would be if you need to drive for 30 minutes, then park it, pop the hood, and rev and let off the engine.

Belt off is a great way to quickly rule a bunch of stuff in or out if you are able to conduct that test. Belt runs the water pump, so you won't be able to drive it 30 minutes, for example. PS too, so don't count on making sharp turns. With no alternator spinning, the battery will be lucky to last 30 minutes. Everything will do fine in park though, for a few minutes.

Have you tried shifting to neutral while it's happening? Shifting gears manually?

Is it definitely coming from the front / engine / front differential area?

And on the "whistling" - I once had a bearing failure that sounded like that - I would have sworn there was gas or liquid involved, but it was a worn bearing (fan bearing on an old Lexus).

Another time, there was a high pitched whistling that would only occur when going over 80 mph and maintaining speed (neither accelerating nor coasting), and it would go away instantly when I'd slightly roll down a window, trying to hear better. I was convinced it was some aerodynamic / air pressure effect. That turned out to be the automatic transmission. . Gave up trying to figure it out, and then we noticed it went away after the AT was replaced. LOL, so now you know why I'm so cautious about believing things.

[IkirisTheX5]

Originally Posted by oldskewel

Bearings can make sounds like that, that come and go very abruptly. The instant on / off is an important clue here. Foot off the gas would let the engine spin down, changing the drive belt tension, which might trigger an alignment shift in a worn, dry bearing, that might turn the sound on instantly.

Is there any way you can recreate the sound while it is parked? If not, that's an important clue too. And it will be tougher to diagnose.

Sounds in general can be really tough to trace. Has the problem progressed to the point where it is exactly predictable when it will occur, and if so, what is the easiest way to get it into that state? For example, easiest would be if you need to drive for 30 minutes, then park it, pop the hood, and rev and let off the engine.

Belt off is a great way to quickly rule a bunch of stuff in or out if you are able to conduct that test. Belt runs the water pump, so you won't be able to drive it 30 minutes, for example. PS too, so don't count on making sharp turns. With no alternator spinning, the battery will be lucky to last 30 minutes. Everything will do fine in park though, for a few minutes.

Have you tried shifting to neutral while it's happening? Shifting gears manually?

Is it definitely coming from the front / engine / front differential area?

And on the "whistling" - I once had a bearing failure that sounded like that - I would have sworn there was gas or liquid involved, but it was a worn bearing (fan bearing on an old Lexus).

Another time, there was a high pitched whistling that would only occur when going over 80 mph and maintaining speed (neither accelerating nor coasting), and it would go away instantly when I'd slightly roll down a window, trying to hear better. I was convinced it was some aerodynamic / air pressure effect. That turned out to be the automatic transmission. . Gave up trying to figure it out, and then we noticed it went away after the AT was replaced. LOL, so now you know why I'm so cautious about believing things.

@Oldskewel: thanks for the thoughtful reply. you definitely answered some of my questions on the dangers of the "belt off"diagnostic approach. I can predict with almost certain accuracy when the noise will begin (+/- 5 mins) and the shit of it is I've never been able to recreate it while stationary. What everyone has suggested about the bearing culprit is really convincing. I may do some research and create a hierarchy of bearing driven components in the M54 engine based on likelihood of failure and just start replacing them one by one.

[bcredliner]

Originally Posted by IkirisTheX5

@Oldskewel: thanks for the thoughtful reply. you definitely answered some of my questions on the dangers of the "belt off"diagnostic approach. I can predict with almost certain accuracy when the noise will begin (+/- 5 mins) and the shit of it is I've never been able to recreate it while stationary. What everyone has suggested about the bearing culprit is really convincing. I may do some research and create a hierarchy of bearing driven components in the M54 engine based on likelihood of failure and just start replacing them one by one.

Never a good idea to try to fix a problem by replacing part by part. Stick with troubleshooting. It's frustrating but don't give up.

Is it correct that the problem never starts until you have been driving for 5 or so minutes? Is it correct that it starts in 5 minutes after starting when the engine is cold? If the noise is present and you let it sit for a half hour does the noise take 5 minutes to come back? It stops when you come to a stop? Does it happen when transmission is in neutral or just when in gear. When is it the loudest or does it always stay the same pitch and volume?

[IkirisTheX5]

No those were actual codes being thrown by the vehicle. Like I mentioned somewhere, it’s possible those 13 faults preceded the noise in question, I just never really checked because with the EGR delete and 180k miles I figured that was just par for the course… or something silly like the O2 sensors I don’t feel pressured to change.