X5 diesel engine noise - With VID.
 

Hi guys. I don't post much on here, but do browse/lurk.

I have a 2009 X5 diesel and I'm trying to diagnose a noise. It sounds like a screeching.. loud scream. I've posted a video and was wondering if someone has heard this before. I've been searching all week and have yet to find something similar. Sorry for the poor quality video, but it's all I could come up with.

any help is greatly appreciated.
the engine light is related to nox sensor replacement.
currently have 210,000 km (130k miles)

https://www.youtube.com/watch?v=PclB_FxEEPM


***EDIT****
Alright, so I thought I would give an update to my issue. Long story short, its not solved yet. But here's what we did do.


Did a smoke test. Everything was good, except... where the wastegate is on the lower turbo. That's where you can see some soot escaping.. So the wastegate bushings/seals are gone.. and Looks like i'll need to pull the turbo off to get it rebuilt or swapped out.

I feel a bit of play. if I hold it closed, the noise goes away. Obviously I don't want to do this long term. I just wanted to see if I could replicate the noise while holding pressure on the wastegate so it doesn't move. Noise could NOT be replicated.

I also scanned for codes with a different machine and was able to get a few more out of it. I'll update the 1st post to show these for others searching.

they are:



4BB3: Nox sensor before denox cat- plausibility nox
4b6a: Nox sensor before denox cat - Plausibility
46B4: NOX Sensor before denox cat plausability nox.
4C04 - I think this could be EGT temp is too high (non-plausible)
4D16 - SCR system, efficiency: Efficiency too low
46A4 - NOx sensor after DeNOx cat., plausibility NOx: NOx signal offset too high at trailing throttle

Bearing or belt. For instance, (water) pump load rises by the square of speed, and your squeak happens at the highest rpm.

How's the tensioner?

Thanks for the reply, I don't think its the belt. (I could be wrong) I feel that its more based on load vs RPM too. At first I thought it was turbo bearing related, but the more i think about it, the more it leads me to believe it isn't. I haven't checked the tensioners. I suppose I could always do that. I would think that if it were the tensioners it would be through most RPM range?

if I drive around normally, (without spirited accelerating) the noise won't come on. You only hear it with a bit of load.

example; I drove to the opposite side of the city yesterday (40-50k round trip) and never once heard it.

Also, depending on load, that screech sound could happen on the lower RPM range. at first I thought it was the small turbo as it went away at 2,000 rpm. but the more I played around with it, I realized it was more dependent on load vs rpm.

Sounds like a turbo issue. Let us know what you learn. Taking it to an experienced indy?

I'm pretty mechanically inclined, I'd probably swap it myself. I just want to narrow it down before I rip it apart.

OK, well you have my best guess, just based on the video. What are the rpms when you detect that "screech". To me it has a metal on metal sound quality. Turbo bearings? I have not experienced a failure with this sound signature.

at first it was upto 2000, but yesterday when I took the video and tried to replicate the sound I noticed it would still do it on higher RPM. I *believe* the small turbo is upto 2000 RPM, and that's when the larger turbo kicks in. I could be wrong tho. That's why originally, I thought it was a high pressure (small turbo) bearing issue.

I'm hoping it's not a turbo issue as I'd probably want to replace both. (if 1 is failing, the other may not be too far behind) which would be quite the job. Replacing the lower turbo looks like 15hr book time for labour. 4.x hours for the small turbo. + the cost for all the parts.

When it does squeel, its only for a second or 2 as you can hear in the vid.

Just a guess but it sounds like a valve whistling. Do these things have bypass valves on the turbos?

Why's the check engine light on?

Have you tried to have someone rev the engine while you try to pin point? You may consider a mechanical stethoscope and touching things around see where's coming from.

It's hard to diagnose noises the internet, but a couple of things coming to mind are the joints in lever controlling the wastegates or the bypass valve that are a little dry or possibly a tear in the membrane of one of said actuators. For example the non-US cars that have a vacuum actuated EGR valve make similar whistle noises when the membrane cracks.