A Cry for Help - Diagnosing a Drive Train Issue

[Leng8093]

Greetings all,

Long time (unregistered) lurker, first time poster in need of some serious help diagnosing a problem with my M4. I have searched high and low on this forum (and beyond) for anyone else who has experienced this issue (I've been to the dealership twice for the issue to no avail [they could not reproduce]) and I've found nothing. Needless to say I'm baffled and hoping I can leverage the vast knowledge and experience of the BMW and F80 community to help diagnose what's gone wrong.

The Problem
A noise (which sounds like a squeaking old mattress -see Exhibit-A for a recording) that was first noticed while I was changing gears in traffic and has progressed since then.

The Car

• 2015 AY M4 6MT

• ~8,600 miles (noise started at ~8,400 miles)

• Dinan Stage 3 ECU - (installed after noise, prior was Stage 2)

• Dinan Heat Exchanger - (installed after noise)

• Dinan CAI

• Dinan Exhaust

• Dinan Suspension

*All mods (with the exception of the heat exchanger) were present on the vehicle thousands of miles prior to the first instance of the sound.

When does it occur?

• Toggling steering wheel M 1 (All Sport+ besides steering) to M 2 setting ("non-sport" settings). Vehicle is stationary, in neutral, with foot brake engaged after 30 minutes of driving. Occurs 80% of the time. Cannot be repeated if you cycle through M 1 and M 2 repeatedly (even immediately after a cold start).

• Lightly blipping/feathering the throttle while in 3rd gear traveling at roughly 22-28 MPH. Car must be driven for at least 20-30 minutes prior before sound occurs (operates normally before then). Sound is constant rather than isolated if throttle is continually feathered to keep in MPH range. Does not occur in any other gear or MPH range. Occurs 80% of the time.

• Shifting from 2nd to 3rd and 3rd to 2nd at roughly 22-28 MPH. Car must be driven for at least 20-30 minutes as there is no sound up to this point (car changes gears normally). This is how I initially noticed the sound but it has since grown to incorporate others. Occurs 85% of the time.

• At cold startup (25% of the time, does not trigger again if you immediately cycle startup)

• Shifting into 1st gear from a stop - Recent development. Car must be driven for 20-30 minutes (car changes gears normally up to that point). Occurs 50% of the time

Sound Captures:

• Exhibit A - captured while switching from M1 to M2 (car stationary in neutral)

• Exhibit B - taken while driving with a friend

• Exhibit D - moving away from the camera

• Exhibit E - shifting into first gear to make a turn

Misc. Characteristics

• No CEL tripped

• No leaks

• Dealership has ostensibly checked the engine bay and found no issues

• Outside of the noise occurring in more frequently (and spreading to different aspects) the car operates normally

Instances where the noise is triggered by the clutch:

• No loss of drive train power

• On clutch being released

• Clutch pedal is not sticky in its range of motion

The noise is not the...
Here's what I can rule out:

• Clutch pedal - this can be moved in and out freely at any time (car on or off) without noise

• Interior cabin - the noise occurs when the car is stationary and I'm intimately familiar with all the rattles.

• Brakes - I have CCBs so I am acutely aware of the unearthly squealing they create while being applied.

• Any manner of timing belt - Timing belts are a very distinctive sound and this not it.

Could it be...

• The clutch - I initially believed that this was the primary culprit as the noise occurred first while switching between 2nd and 3rd gear (both up and down shift) at the specific MPH range. But why not in any other gear change (say 4th to 5th?) or any other speed?

• The throttle - I'm now suspecting that this may be the issue due to the recent development of the sound being triggered by switching between M 1 and M 2 after being driven for 20-30 minutes. Also, lightly blipping and feathering the throttle while in 3rd gear travelling at 22-28 MPH and having the sound constantly occur over a prolonged period leads me to believe that it is not the clutch as the vehicle is already in gear. But if it's the throttle, then why doesn't it occur in any other gear or speed?

• Suspension - the noise sounds an awful lot like a squeaky suspension but then again if that were the case, it should occur constantly, regardless of gear, speed, and quality of road surface rather than the specific 3rd gear characteristic.

Once again, any help that can be provided will really help me out as I'm at a complete and total loss what to do. Thanks again!

[lukej]

I can't hear the sound clips ,,, maybe just my iPad,,

What out hearing it,, just a guess,, do you have the Carbon Roof?

Is coming from a misaligned joint of the carbon fiber roof?.

[smithf80]

All of your videos are set to private.

[Leng8093]

Sorry all, reset the videos so hopefully they can be viewed.

[jmg]

Your M1 to M2 toggling is the biggest tell and the easiest way to diagnose.

Reprogram your M1 to have the M Adaptive to default instead of sport. Recreate the conditions in which toggling to M2 triggers the sound. Did it happen again? If the sound disappears, then it's most likely related to your suspension. Do this a few times to make sure that the results are consistent enough to make the correlation. When you are convinced, go back to stock suspension and see if the problem goes away with M1 suspension is set to Sport+. Problem solved. Contact Dinan about replacing your parts, it's warrantied by Dinan.


If the sound doesn't go away, do the same thing for the transmission, steering, and throttle. Steering might be different for you since you are in non-sport in M1.

If you find that the throttle setting has an effect on the sound, then it might be your exhaust, or more precisely the exhaust flap that opens up the other side of the exhaust. When in efficient mode, the flap opens and closes during certain instances of throttle. It's open full time in sport or sport+ mode. Does the sound appear when in sport modes? If it does, you could rule it out since it doesn't move in those modes. Have your shop look at that exhaust and check to see that the flap is operating properly.

Anyway good luck, and if you do solve the issue please keep us informed!

[Msmall143]

rock in the dust guard?

[Leng8093]

Originally Posted by lukej

I can't hear the sound clips ,,, maybe just my iPad,,

What out hearing it,, just a guess,, do you have the Carbon Roof?

Is coming from a misaligned joint of the carbon fiber roof?.

I do have a carbon fiber roof, however the sound seems to be coming from under the vehicle rather than above. A good suggestion though that I'll double check.

[jwzimm]

I am betting he is hearing the exhaust valves open or close when switching from efficient to sport+.

[Leng8093]

Originally Posted by jmg

Your M1 to M2 toggling is the biggest tell and the easiest way to diagnose.

Reprogram your M1 to have the M Adaptive to default instead of sport. Recreate the conditions in which toggling to M2 triggers the sound. Did it happen again? If the sound disappears, then it's most likely related to your suspension. Do this a few times to make sure that the results are consistent enough to make the correlation. When you are convinced, go back to stock suspension and see if the problem goes away with M1 suspension is set to Sport+. Problem solved. Contact Dinan about replacing your parts, it's warrantied by Dinan.


If the sound doesn't go away, do the same thing for the transmission, steering, and throttle. Steering might be different for you since you are in non-sport in M1.

If you find that the throttle setting has an effect on the sound, then it might be your exhaust, or more precisely the exhaust flap that opens up the other side of the exhaust. When in efficient mode, the flap opens and closes during certain instances of throttle. It's open full time in sport or sport+ mode. Does the sound appear when in sport modes? If it does, you could rule it out since it doesn't move in those modes. Have your shop look at that exhaust and check to see that the flap is operating properly.

Anyway good luck, and if you do solve the issue please keep us informed!

A hell of a response which is full of great information. Let me run through a couple of runs to test the variables of each M setting. I'll be out this weekend but I'll definitely report back.

[smithf80]

Originally Posted by jwzimm

I am betting he is hearing the exhaust valves open or close when switching from efficient to sport+.

Intersting thought.

[paliknight]

Originally Posted by Msmall143

rock in the dust guard?

thats what i initially thought he was hearing, but thats not what his videos sound like.

Originally Posted by jwzimm

I am betting he is hearing the exhaust valves open or close when switching from efficient to sport+.

thats strange because when i switch i dont get the noise he does.

it does sound like the suspension though.

[jmg]

Originally Posted by paliknight

thats what i initially thought he was hearing, but thats not what his videos sound like.


thats strange because when i switch i dont get the noise he does.

it does sound like the suspension though.

Yeah, your not supposed to hear anything like that. The only thing I hear is the exhaust just gets super loud.

Based on what the OP has told us so far, my money is on the exhaust flap with the Adaptive Suspension in second.

[jmg]

Originally Posted by Msmall143

rock in the dust guard?

I don't think so. That sound is a lot more terrifying for some reason.

[SakhirM4]

Do they not have a dealer in Seattle?

[Leng8093]

Originally Posted by SakhirM4

Do they not have a dealer in Seattle?

There's a dealership in Seattle, which I've been to twice, but they could not reproduce the issue. I've just recently sent the service advisor the recordings as well and they state it's probably an issue with the brake rotor rubbing against the dust guard. The issue I'm facing as an owner who isn't super car savvy is, although I respect their input as experts, my gut doesn't think that is the issue.

*Edited to add: Of course, no disrespect to the dealership intended as it's not a straight forward issue I'm having.

[nicknaz]

OP, can you time it so that a tech or shop foreman rides in your car after 20-30 min of driving so you can replicate the noises right then and there? Get a nice loaner while they fix and call it a day

[jmg]

Originally Posted by Leng8093

There's a dealership in Seattle, which I've been to twice, but they could not reproduce the issue. I've just recently sent the service advisor the recordings as well and they state it's probably an issue with the brake rotor rubbing against the dust guard. The issue I'm facing as an owner who isn't super car savvy is, although I respect their input as experts, my gut doesn't think that is the issue.

*Edited to add: Of course, no disrespect to the dealership intended as it's not a straight forward issue I'm having.

I really don't think it's a rock in the dust guard since it sound different than what I am hearing in the video. Then again, it's a video and not the best quality. Regardless, in my experience, service advisors are schedulers and customer service representatives. Their guess is not based on hands-on technical skill, but on experience with other clients and their cars. I never take their advice with any real merit. No offense to them either, but it's not their job. They are service advisors, not service technicians.


But who knows, maybe they are right? I hope they are right, because that is an easy fix.

[Leng8093]

Originally Posted by nicknaz

OP, can you time it so that a tech or shop foreman rides in your car after 20-30 min of driving so you can replicate the noises right then and there? Get a nice loaner while they fix and call it a day

100% spot on. My second visit I requested that very thing and, to the dealerships credit, they sent a foreman along for a ride who acknowledged the noise but the diagnosis and resulting scope of work (replaced a belt related to the clutch -going off memory) did not resolve the issue.

[Leng8093]

Originally Posted by jmg

I really don't think it's a rock in the dust guard since it sound different than what I am hearing in the video. Then again, it's a video and not the best quality. Regardless, in my experience, service advisors are schedulers and customer service representatives. Their guess is not based on hands-on technical skill, but on experience with other clients and their cars. I never take their advice with any real merit. No offense to them either, but it's not their job. They are service advisors, not service technicians.


But who knows, maybe they are right? I hope they are right, because that is an easy fix.

I'm picking up what you're throwing down, buddy. Spot on.

[BitchinManWheels]

My vote is exhaust valve flap.
I have the macht schnell evc module thus able to open and close the flap at will. It is louder than most think. Yours may be extremely squeaky.
How to rule this out for sure is simply disconnect the flap motors then drive the car around and see if you can reproduce the sound.
BTW, I have the Dinan S2 with CAI, exhaust, & suspension too and I leave the valves open all the time!

[GrussGott]

Originally Posted by BitchinManWheels

My vote is exhaust valve flap.
I have the macht schnell evc module thus able to open and close the flap at will. It is louder than most think. Yours may be extremely squeaky.
How to rule this out for sure is simply disconnect the flap motors then drive the car around and see if you can reproduce the sound.
BTW, I have the Dinan S2 with CAI, exhaust, & suspension too and I leave the valves open all the time!

yeah, like the others, my two thoughts were the exhaust flaps & suspension ... jmg has a nice trouble-shooting idea for the suspension, but I'd be tempted to try the exhaust flap first: just pull the plugs with the flaps open and see if you never hear the sound again. Easy to do and rules it out 100%.

The 20-30 "warm up" to the noise would make sense in that the parts are heating up and expanding which exacerbates the squeak.

That said, in the second video the squeak happens a few times in a row at very low RPMs and I didn't think the flaps would open/close that much with nothing else going on. (btw, I know the 6MT is different but I can't imagine driving my DCT in 3rd at ~25 MPH)

Unless those exhaust flaps open/close a hell of a lot more than seems reasonable I'm leaning towards suspension and one of the actuators/electric value-y type things: it heats up with road use, then squeaks, but when you try to cycle from M1 to M2 and back you essentially heat-lube the parts and they don't squeak anymore.

[Leng8093]

Originally Posted by GrussGott

yeah, like the others, my two thoughts were the exhaust flaps & suspension ... jmg has a nice trouble-shooting idea for the suspension, but I'd be tempted to try the exhaust flap first: just pull the plugs with the flaps open and see if you never hear the sound again. Easy to do and rules it out 100%.

The 20-30 "warm up" to the noise would make sense in that the parts are heating up and expanding which exacerbates the squeak.

That said, in the second video the squeak happens a few times in a row at very low RPMs and I didn't think the flaps would open/close that much with nothing else going on. (btw, I know the 6MT is different but I can't imagine driving my DCT in 3rd at ~25 MPH)

Unless those exhaust flaps open/close a hell of a lot more than seems reasonable I'm leaning towards suspension and one of the actuators/electric value-y type things: it heats up with road use, then squeaks, but when you try to cycle from M1 to M2 and back you essentially heat-lube the parts and they don't squeak anymore.

UPDATE:

Did some thorough testing yesterday (as jmg suggested - big shout out!) and, long story short, it was toggling the M throttle in anything other than "efficient" mode which causes the sound.

Specifically, what I did was drive the car around in default, non-M settings (40 minutes of driving) and, lo and behold, no sound at all, everything was perfect. Next, I went through the individual M settings and tested each in isolation against the sound producing criteria, suspension, steering, MDM -all passed except the exact moment I adjusted throttle from "efficient" to either "sport" or "sport+", bam! There it was!

Car's currently at the dealership and, after test driving with the shop forman (he didn't have an idea off the top of his head why this would be occurring), my fingers are crossed they now can squash this issue once and for all.

Big thank you for all the input and suggestions I've received from everyone! Absolutely invaluable in lending me a hand to track this issue down!

As an aside, any thoughts of what it could be in the engine that the M throttle setting adjusts (exhaust valves as was previously suggested)?