Main Bearing, Vanos, or Something Worse?

Dear M3Post brain trust, I need to tap into the Forum hive mind expertise to try and understand the possible root cause of a nasty engine (?) noise my car has developed. I’ve already spent months trying to diagnose the issue as well as $2700 in parts and professional labor. Below are all of the details. I’ll try to be as descriptive as I can.

Car Details:
2008 E92 M3, DCT (08/2008 build date)
145,000 miles
One owner (me)
BE Bearings & BE (ARP) bolts done at 118K miles
Throttle Actuators done
New alternator recently done
Vanos spring covers NOT done yet

Symptoms:
The noise sounds like bad metallic engine rattle, similar to detonation, like a ball bearing rattling in a can. It’s worst when cold, when in first or second gear, at medium throttle input, and when tuning sharp right corners. The metallic rattle noise will also manifest at WOT in a straight line in first and second gears, and less so at WOT in third gear. But it’s inconsistent in a straight line, can not be heard at idle, and almost sounds like something metallic is catching - like a slipping ratchet - or something lose inside the valve cover. Under normal light throttle driving around town, or on the highway, the noise is not present. When the car is stationary and in neutral, the noise is not present when idling or revving the motor.

Mitigation Efforts So Far:
Read DME codes = No codes present and no CEL
3 gallons of E85 added to a full tank of 93 E10 - No effect on the noise
Re-flash to OEM tune = No effect on the noise
Re-install OEM exhaust with new header donut gaskets = No effect on the noise
Replace both timing chain tensioners = No effect on the noise
Replace all 4 Vanos solenoids = No effect on the noise
Change engine oil and filter = No effect on the noise
Inspected old oil filter pleats and oil catch basin for metallic flecks = None found

Originally I thought it was detonation, which it isn’t after testing with E85 + 93E10 and re-flashing back to the OEM tune file. Next I thought it was the timing chain, so I replaced both chain tensioners with no effect. Next I thought it was Vanos rattle, so I replaced all 4 Vanos solenoids, with no effect on the noise.

I was able to record a sound file of the noise when driving in a circle with a fairly cold engine. You can hear the sound at the link below, and it’s best to listen to the sound file with ear buds at about 2/3rd volume level. It sounds like ball bearing rattling in can. The noise is “on top” of the engine note, which is why I suspected timing chain tensioners or Vanos solenoids, but to no avail. Perhaps it’s the Vanos spring mechanism or something loose inside the valve cover? But there is no noise when the car is standing still, in neutral, under no load, idling, or revving the engine?

Sound File Link Below: All help and advice is appreciated.
https://soundcloud.com/user-90547482/s65-engine-rattle-noise-vanos

DrFerry wrote

Dear M3Post brain trust, I need to tap into the Forum hive mind expertise to try and understand the possible root cause of a nasty engine (?) noise my car has developed. I’ve already spent months trying to diagnose the issue as well as $2700 in parts and professional labor. Below are all of the details. I’ll try to be as descriptive as I can.

Car Details:
2008 E92 M3, DCT (08/2008 build date)
145,000 miles
One owner (me)
BE Bearings & BE (ARP) bolts done at 118K miles
Throttle Actuators done
New alternator recently done
Vanos spring covers NOT done yet

Symptoms:
The noise sounds like bad metallic engine rattle, similar to detonation, like a ball bearing rattling in a can. It’s worst when cold, when in first or second gear, at medium throttle input, and when tuning sharp right corners. The metallic rattle noise will also manifest at WOT in a straight line in first and second gears, and less so at WOT in third gear. But it’s inconsistent in a straight line, can not be heard at idle, and almost sounds like something metallic is catching - like a slipping ratchet - or something lose inside the valve cover. Under normal light throttle driving around town, or on the highway, the noise is not present. When the car is stationary and in neutral, the noise is not present when idling or revving the motor.

Mitigation Efforts So Far:
Read DME codes = No codes present and no CEL
3 gallons of E85 added to a full tank of 93 E10 - No effect on the noise
Re-flash to OEM tune = No effect on the noise
[...]

I hear 2 noises and I want to verify what we are talking about. The noise on top that sounds like gravel or the engine noise under that, which has a metallic sound?

Brandoch wrote

I hear 2 noises and I want to verify what we are talking about. The noise on top that sounds like gravel or the engine noise under that, which has a metallic sound?

The sound track has some other ambient sounds of hands on the steering wheel - like a sticky noise you may be referring too. So it's not the gravel sound, but definitely embedded within the engine noise to my ear IMO. On the sound track I hear it best within the 10 sec to 18 sec segment. Hope this helps. Thanks for your interest.

Has any acoustic diagnostics been performed on the DCT flywheel?

No faults stored across modules when checked with ISTA?

Hi Dr Ferry

We lost an engine due to main bearing failure (or poor tuning, who knows) and it did not sound anything like that.

If you haven't done the vanos covers, you may want to at least inspect them. I expect you will find deep grooves in the metal there where the springs are just eating into the head.

These engines make lots of noises, but that noise doesn't sound normal at all. Something is up.

DrFerry wrote

The sound track has some other ambient sounds of hands on the steering wheel - like a sticky noise you may be referring too. So it's not the gravel sound, but definitely embedded within the engine noise to my ear IMO. On the sound track I hear it best within the 10 sec to 18 sec segment. Hope this helps. Thanks for your interest.

Things I'm thinking of, not necessarily helpful.
*power steering pump, have you tried to run without belts on?
*vanos springs rubbing if the covers have blowen off
*valve springs are broken but not yet causing miss fires
*collapsed motor mount on left side causing rubbing or stress
I would love a louder sound track. Have you used a stethoscope to isolate the noise?

deansbimmer wrote

Has any acoustic diagnostics been performed on the DCT flywheel?

No faults stored across modules when checked with ISTA?

An acoustic diagnostic has NOT been performed on the DCT flywheel. I had no idea the flywheel could be the culprit. Is the acoustic analysis something only the Dealer can do? The codes were read via OBD 2 port today, and I was told no codes were present. I'll check again with the Mechanic regarding the other modules. Many thanks for your input. If you have time can you shed a little more light on the DCT flywheel possibly being the culprit?

Am I understanding correctly, that the only time the noise is present, is when there is a load being applied to the chassis, either forward or laterally?

SYT_Shadow wrote

Hi Dr Ferry
We lost an engine due to main bearing failure (or poor tuning, who knows) and it did not sound anything like that. If you haven't done the vanos covers, you may want to at least inspect them. I expect you will find deep grooves in the metal there where the springs are just eating into the head. These engines make lots of noises, but that noise doesn't sound normal at all. Something is up.

Thank you for your insights. I agree something is up indeed! I didn't know the Vanos springs can eat into the head, but I suppose if one had come un-clipped from one of the pegs it would do that. It's odd that in higher gears under WOT it doesn't make the noise and the 'right hand corner are worse' aspect has me scratching my head. Thanks again for your feedback.

Davisca455 wrote

Am I understanding correctly, that the only time the noise is present, is when there is a load being applied to the chassis, either forward or laterally?

Correct. When under acceleration or medium throttle in 1st and 2nd and worst when turning right. No noise when idling, or in neutral when revving the motor.

Brandoch wrote

Things I'm thinking of, not necessarily helpful.
*power steering pump, have you tried to run without belts on?
*vanos springs rubbing if the covers have blowen off
*valve springs are broken but not yet causing miss fires
*collapsed motor mount on left side causing rubbing or stress
I would love a louder sound track. Have you used a stethoscope to isolate the noise?

Not tried running w/o belts yet. You're the second person who has mentioned Vanos springs rubbing! Yikes! Interesting idea to check the left side engine mount (it's a Vibra Technics mount). I had a valve spring break once upon a time on my '95 Supra TT and while similar in sound, it's not quite the same. But I suppose it's still a possibility - though broken valve springs usually tick at idle. I've not used a stethoscope because the car has to be moving to manifest the noise i.e. no noise present at idle. Sorry the sound file is not loud enough. I have a short video clip, but have not posted it to YouTube because the indicated speeds are quite high on a public road... I'll think about posting it.

I would not expect to hear the noise persist if it was knock. The DME is aggressive about protecting the engine by pulling timing and shutting down cylinders. You would be immediately down on power if it was knock.

Coming from the Subaru world I’m probably the worst person to ask about rattles since I am trained to ignore them for the most part.

The conditions you state for the noise makes me think either power steering or engine mounts. I cannot hear it or am still too new to the platform to discern the sound you’re describing. I also have a low level of tinnitus from doing dumb things in my youth.

Boy, this is an odd one.

Of note, you'll generally need ISTA to get faults on all modules. Generic readers sometimes cant get them all.

I'd take a hard look at the motor mounts. They will be the most stressed under load in lower gears, and the symptoms can change when turning.

I broke a motor mount in one of my rx-7s back in the day, and the symptoms were similar. I dont know how this would sound like in this chassis.

Regarding vanos springs, you can at least peak at the passenger side by opening the oil cap.

If the concern is ignition-knock, I don't hear anything of note. I listened with headphones on at max volume, too. (To me it just sounds like interior creeks when chassis is flexing)

As for rod-knock, I don't hear anything neither as per the quality of the recording.


Couple of things to note.
1. If you are using stock tune, then I would expect stock knock/misfire strategy implemented.
2. If you suspect VANOS springs/covers, you can take a peek thru the oil cap to at least look at the bank 1 VANOS cover condition.
3. If you suspect something very metallic going on inside the engine, did you look thru the oil filter pleats for any notable debris?

It'd be nice to get some data. Can you get a graph of ISTA when this concern is happening?

Wow this one is indeed a mystery!

My initial impressions are:
- Doesn't sound rpm related, so I feel that rules out bearings, belts, etc

- VANOS spring error should throw codes, and it sounds a bit too intermittent to be that

- As someone said, it sounds more like a creaking sound. If it occurs more when you're turning, it might be something chassis or mounts related.

- I've had bad experience with VT mounts, so I'd definitely check those.

- I'd also check that all suspension and subframe bolts are tight.

- Also check any underbody panels and heat shields to make sure there are no missing clips/screws and the heat shields aren't contacting/rubbing against something. Those have caused weird noises for me in the past.

Good luck!

I'll bet you won't find anything in ista. This sounds so mechanical.

For the engine mounts, with the car on a lift it's as easy as trying to flex the engine supports with a crowbar and you'll know quickly.

The oil pan will also damn near touch the belly pan if the engine mounts are toast.

RocketyMan wrote

3. If you suspect something very metallic going on inside the engine, did you look thru the oil filter pleats for any notable debris? It'd be nice to get some data. Can you get a graph of ISTA when this concern is happening?

Both myself and my mechanic looked at the old oil filter paper pleats, as well as inside the oil catch basin, for any shiny metal flecks or metallic dust. We found none. Thanks for your input, ideas and feedback.

Unfortunately, I don't posses the ISTA software. Getting a high quality sound clip has proved to be quite difficult. I strapped a GoPro under the hood, but there was so much other noise inside the engine bay when driving, the mechanical knocking / rattling sound was drowned out. Recording with my iPhone inside the cabin yielded the current recording sound track, but even then the sound track is polluted with ambient sounds of hands on steering wheel (sounds like a sticky tacky sound) and other low frequency booming noise inherent in the E9X chassis.

The human ear can isolate the sound. My mechanic and I had no problem hearing it this morning when I picked up the car. The engine was cold so we drove across the road to a parking lot and the noise was present when driving in clockwise circles but not in anti-clockwise circles.

DrFerry wrote

Both myself and my mechanic looked at the old oil filter paper pleats, as well as inside the oil catch basin, for any shiny metal flecks or metallic dust. We found none. Thanks for your input, ideas and feedback.

Unfortunately, I don't posses the ISTA software. Getting a high quality sound clip has proved to be quite difficult. I strapped a GoPro under the hood, but there was so much other noise inside the engine bay when driving, the mechanical knocking / rattling sound was drowned out. Recording with my iPhone inside the cabin yielded the current recording sound track, but even then the sound track is polluted with ambient sounds of hands on steering wheel (sounds like a sticky tacky sound) and other low frequency booming noise inherent in the E9X chassis.

The human ear can isolate the sound. My mechanic and I had no problem hearing it this morning when I picked up the car. The engine was cold so we drove across the road to a parking lot and the noise was present when driving in clockwise circles but not in anti-clockwise circles.

Power steering or engine mounts, that's my guess.

Does the car have an aftermarket skid plate on it? If so, which one?

drwankel wrote

Does the car have an aftermarket skid plate on it? If so, which one?

No aftermarket skid plate. Just the OEM plate and OEM front felt piece.

Thanks to all of you for replying, and providing some very insightful comments. Here's what's resonated with me the most so far from those comments - and after living with the noise since late July.

1) Loose Vanos spring(s) grinding into the head or valve covers
2) Broken Vibra Technics engine mount(s)
3) Loose heat shield(s)?

I took a peek into the passenger side valve cover after removing the oil filler cap. I could easily see one OEM Vanos black plastic covers which looked intact with no cracks. It was hard to see the other one.

The car means a lot to me. I've had her for 16 years since new, and we've been through thick and thin together (long story). She's an old girl now, but doesn't look her age. I'm not sure what I'd do without her. I've had other fun cars before her, and regretted selling them. We'll figure this out, though it may take a while. She's a keeper.