[Holtdahooligan]

I would like to start off by stating that this is NOT wastegate rattle, the easily diagnosable sound we all know and hate.

So, guys, what is going on with my motor? I took my car to a local indy bimmer shop and even they couldn't figure it out. They removed the valve cover and said everything looked fine. No gold look to the cam ledges, chain was tight and guides in good shape.

This has been going on for about 6 months now. I haven't noticed any decrease in engine performance and haven't gotten a single code. I'm full bolt on with inlets and e60 MHD flash (09 135i MT). My N54 motor currently has 102,500 miles on it.

It sounds like some kind of oil starvation/valve train wine and only happens on deceleration. It doesn't matter whether or not the oils hot or cold. Engine braking from any rpm over about 3k will cause this loud decel noise. No, this isn't wastegate rattle.

This first video is with the windows up and oil up to temp, replicating the sound once.

This second video is with the windows down, oil not fully warm and I'm able to replicate the noise twice.

Please note that the noise I am referring to is not the BOV purging or turbo spoil sounds. I'm talking about the aggressive chain-like chattering sound as the RPMS fall.

I have attached an oil analysis which did show higher than average levels of Tin and Lead. This analysis was done at 101,256 miles with 2,233 miles on the oil.

I haven't found anything similar to this sound online and could really use some help. Does anyone have a clue what it could be? Thanks for your time!

[Had0uken!]

Crankshaft?

I'm not a mechanic or engineering minded in any way - I had a metallic clanging/rattle on mine (not wastegate at this point) when letting off throttle/decelerating and occasionally when blipping throttle.

Luckily car was still under warranty - took into Bmw (suspecting wastegate rattle as that was the only rattle info I could find online). Turns out it was the crankshaft - a bearing had spun or something. they didn't know why, put it down to oil starvation or just manufacturing defect. Sorted out under warranty thankfully.


Hopefully it's not that for you, again could be completely off the mark but this is my experience.

[dyezak]

Is this issue only replicable while driving? Can you not replicate the sound while in park or neutral? I watched both videos and I don't think it's speed related, or RPM related, it seems only related to decel in low load situations (i.e. in gear). Does that seem correct?

[Holtdahooligan]

Originally Posted by dyezak

Is this issue only replicable while driving? Can you not replicate the sound while in park or neutral? I watched both videos and I don't think it's speed related, or RPM related, it seems only related to decel in low load situations (i.e. in gear). Does that seem correct?

You are correct. The sound is only replicable during decel under load (in gear). Indy shop could only replicate the sound when driving the car but not while on a lift. Thank you for reminding me of this.

[dyezak]

I've never seen/heard anything like that before so I'm just going to throw some ideas out and see what sticks. If this is load related, but definitely with the engine, then that does help narrow things down. I don't think it can be anything with the belt drive or accessories. But it could be the timing chain or tensioning system. It could be the vanos system. Not likely to be valvetrain. Possibly a REALLY bad PCV failure?? Any oil consumption?

Again, I'm not sure, just seeing if anything gets the juices flowing and helps you figure it out.

[MysticRob]

Originally Posted by Holtdahooligan

You are correct. The sound is only replicable during decel under load (in gear). Indy shop could only replicate the sound when driving the car but not while on a lift. Thank you for reminding me of this.

If I'm hearing the vids correctly it sounds like an almost metallic, and very rapid, high rpm whine that spools down slowly.

Since you have inlets, I wonder if they are unmasking the sounds of the turbos themselves. With such a fast whine I'm thinking that's what I'm hearing.

Curious if it would still be as audible without the inlets.

[dyezak]

Originally Posted by MysticRob

If I'm hearing the vids correctly it sounds like an almost metallic, and very rapid, high rpm whine that spools down slowly.

Since you have inlets, I wonder if they are unmasking the sounds of the turbos themselves. With such a fast whine I'm thinking that's what I'm hearing.

Curious if it would still be as audible without the inlets.

I've ran fully open turbos before in single top-side setups with no filter at all and never heard that. But it's possible I guess if the thrust bearing was shot.

[austin]

Do you have a gopro that you can mount somewhere else on the car in hopes of capturing the sound a bit more clearly? Maybe under the hood or something.

It almost sounds like a rattle outside the engine... There's an exhaust clamp after the downpipes that is metal on metal. It's so easy to get to you could check if it's loose real quick.

Otherwise it's really hard to tell through the video...

It seems to make the noise at ~3k RPM; if you hold it there with no load will it make the noise? If not it is unlikely to be the timing chain or an accessory, because they don't care if the car is accelerating or decelerating. They only care about the speed of the engine, and acceleration in terms of RPM/time, not the acceleration of the car.

good luck

[STR8-6IX]

if the engine sounds fine under heavy load/ high RPM, and you cannot replicate the sound when the engine is not under load, I am starting to thing it is not the engine. possibly driveshaft, maybe transmission? something drivetrain related.

the Indy checked the motor and found it to be in good shape right? great choice on the oil/weight BTW. you know whats good when it comes to FBO.

[dyezak]

Originally Posted by STR8-6IX

if the engine sounds fine under heavy load/ high RPM, and you cannot replicate the sound when the engine is not under load, I am starting to thing it is not the engine. possibly driveshaft, maybe transmission? something drivetrain related.

the Indy checked the motor and found it to be in good shape right? great choice on the oil/weight BTW. you know whats good when it comes to FBO.

It's RPM related not speed related (watch the vids). RPM related means engine every time. It's just that it needs to be under heavy decel (i.e. extremely light load) that can't be recreated free-revving.

[austin]

I wouldn't be so quick to rule out a drivetrain issue. When in gear, engine RPM is tied to drivetrain RPM. So it could be that at a certain RPM something in the drivetrain is rattling, like the DMFW or the driveshaft carrier bearing. I've heard trans input shafts make some weird rattles too.

I'm not saying it necessarily is outside the engine, but I wouldn't rule it out entirely from a 10s video either.

[Holtdahooligan]

I really appreciate the suggestions and input guys. Only views and crickets from n54tech.

Belt and pulleys were replace ~500 miles ago so that's out. Water pump replaced ~1k ago.
I did have a slight chain "slapping" noise at idle back in january. A tech friend suggested a worn tensioner bolt, cleared that right up. Never got codes for this but replaced both Vanos solenoids just in case.

I do have oil consumption that increase with long highway trips (drinks 1qt every 3k miles). I have the RB upgraded pcv valve, replaced the plastic flapper hose and installed a catch can which has collected next to nothing over the years.

Running w/o primary and secondary cats, stock resonator and muffler delete. Friends have driven behind me and noted zero smoke from the exhaust during normal driving or WOT pulls. They have however seen small puffs of smoke under hard decel (*where I'm hearing my sound). Downpipe V- band clamps are not loose.

Don't believe it's drivetrain related. Transmissions been out, bolts, clutch, flywheel, mounts, driveshaft, differential have all be replaced. I know you can't tell from the videos but the sound is specifically coming from the from under the hood. I will attempt to borrow a GoPro and get a video from under the hood soon.

The noise only happens when in any gear, car moving at any speed and engine breaking from above 3k rpms. Not replicable while holding at a constant rpm, in neutral or with car in gear on a lift.

[NoQuarter]

Does engine movement change appreciably when slowing down under load vs steady state/accelerating?

In other words... Instead of tilting left it tilts right further than it should be?

[Holtdahooligan]

Originally Posted by NoQuarter

Does engine movement change appreciably when slowing down under load vs steady state/accelerating?

In other words... Instead of tilting left it tilts right further than it should be?

Are you referring to the motor mounts being shot? I just last month installed the Ad engineering motor mounts. The car made the same noise before and after.

[Vincent_E90]

Keep me updated. Mine started to do this over the weekend a couple times. I tried to get it to do it again after work today but couldnt replicate it. Mine usually happens pre-boost and sometimes in decel like yours.

FBO, with catless downpipes. I am thinking it is the turbine catching but. Similar to you, no heavy smoke coming out.

How many miles on your turbos?

[dyezak]

A good option would be to go to a shop with a dyno and replicate the issue on the dyno with the hood popped so you can find the source. It'll cost dyno time, but it'll shorten the time to resolution.

ETA - I saw your thread on n54tech but only answered here because there's no reason for me to do double work

[NoQuarter]

Broken bolts ? Maybe between engine and bellhousing?

[Vincent_E90]

Here's my sound, pretty similar

Sound starts around 7 seconds.

Over the weekend it was happening more on accelerating at 1/2 or 3/4 throttle passing 2500-3000rpm, I was not able to replicate it when recording yesterday after work. But caught it on video this morning coming in to work.

[Vincent_E90]

Was able to get a videos of the sound from idle.. This one you can hear throughout the video from under the car.

This one starts at ~37 seconds in.

are these similar to what you are hearing? Mine are at idle and can hear better from the side/under the car rather than the front.

I am thinking about checking my downpipes this weekend for a loose connection on the v bands. if they're all snug I am going to take them off and inspect them for any oil residue.

What actions have you done already?

[STR8-6IX]

I have noticed it is quite common for the n54 to smoke on decel. I suggest this is what you look into regarding your problem.

sorry I could not be of more help

[dyezak]

Originally Posted by STR8-6IX

I have noticed it is quite common for the n54 to smoke on decel. I suggest this is what you look into regarding your problem.

sorry I could not be of more help

That's generally the crappy pcv system.

[rismo]

Probably your downpipes hitting some heat shield.
Weight distribution changes under decel.

At least I had this a couple of times when the DP's were a bit off...
Also can happen when re-aligning etc...

Hope this helps...