Main Bearing, Vanos, or Something Worse?

If you've had the sound since July then I don't think it's #1. Loose VANOS springs will definitely cause an error eventually.

You’re in a thread about broken VT engine mounts with Redd, I don’t know why you didn’t start with those POS mounts. A quick search here pulls up lots of posts about them breaking.

spammysammich wrote

You’re in a thread about broken VT engine mounts with Redd, I don’t know why you didn’t start with those POS mounts. A quick search here pulls up lots of posts about them breaking.

I was aware the VT mounts can fail but hadn’t associated the rhythmical knocking noise with the engine mounts (sounds almost like something loose inside the valve cover). Piston slap also comes to mind. In the cabin the noise sounds like top end. Hence engine mounts didn’t occur to me. I've read some of the threads about VT mount failures but I don't recall engine knocking / rattling being mentioned. PS: I understand about low grade tinnitus because I have it too. But I encourage you to take a listen to the sound track recording again with focus on the 10 sec to 18 sec segment. The knocking noise is "on top" of the engine noise. Thanks for all of your help and expertise.

spammysammich wrote

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

Good catch. I found a video of someone with an E92 M3 who chronicles broken engine mounts causing the motor to drop and rub on the belly pan. I have yet to remove the belly pan and see if the noise stops.
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Yikes! That could very well be a culprit to your metallic "noise." This would also coincide when you take certain turns that you hear it more than otherwise.

In my experience, you should be able to fit your fingers between the rear sump and the belly pan. These oil pans are not cheap. They're a cool $1500 new.

RocketyMan wrote

Yikes! That could very well be a culprit to your metallic "noise." This would also coincide when you take certain turns that you hear it more than otherwise. In my experience, you should be able to fit your fingers between the rear sump and the belly pan. These oil pans are not cheap. They're a cool $1500 new.

I found a post by Bubbles in Redd's Vibra Technics thread where he mentions an engine knock rattle being caused by the mounts! The evidence is stacking up. I'm thinking about removing the skid plate to see IF the noise goes away.

https://www.m3post.com/forums/showpost.php?p=27176486&postcount=18
and
https://www.m3post.com/forums/showpost.php?p=27168627&postcount=2

There are warnings in TIS to not drive the car without the belly pan it is a stressed member.

spammysammich wrote

There are warnings in TIS to not drive the car without the belly pan it is a stressed member.

The engine will probably fall through the hole knowing my luck... Thanks for the information though.

Those engine mounts don’t collapse as stock mounts will and give you the telltale engine sag but they may have delaminated and you might see that by observing how the engine rocks when somebody revs it in neutral. Or watch the engine closely as somebody turns it over. Blown mounts should produce a noticeable wobble. Fresh mounts twist a little and recover quickly.

spammysammich wrote

Those engine mounts don’t collapse as stock mounts will and give you the telltale engine sag but they may have delaminated and you might see that by observing how the engine rocks when somebody revs it in neutral. Or watch the engine closely as somebody turns it over. Blown mounts should produce a noticeable wobble. Fresh mounts twist a little and recover quickly.

In the posts I linked above (a couple of posts up) comments are made about the VT mounting nuts coming undone and causing rod bearing type noises - as well as the rubber inserts delaminating - just as you mentioned. In that thread Vibra Technics mounts failed in less than 5K miles! Anyway, because the VT mounts have a solid aluminum cylinder design, I'm thinking if the mounting nuts come loose a rattle noise could definitely happen - just as mentioned by Bubbles

DrFerry wrote

Good catch. I found a video of someone with an E92 M3 who chronicles broken engine mounts causing the motor to drop and rub on the belly pan. I have yet to remove the belly pan and see if the noise stops.
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Stock mounts are full rubber and may collapse enough to allow the oil pan to contact the belly pan. VT mounts have a metal housing, so may not allow the engine to droop enough to be visible from the belly pan. Best is to eyeball the mount, or remove it to check.

Just a quick update: My car is going in (https://www.schallmotorsport.com/) for engine mount replacement on February 10th, '25. The current Vibra-Technics engine mounts will be replaced with OEM BMW engine mounts. The issue has become slightly worse, because now I can hear the rattle at cold start idle and I notice the vibration through the steering wheel (column) a bit more too. Oh well, I'll know pretty soon if the engine mounts were the culprit(s).

DrFerry wrote

Just a quick update: My car is going in (https://www.schallmotorsport.com/) for engine mount replacement on February 10th, '25. The current Vibra-Technics engine mounts will be replaced with OEM BMW engine mounts. The issue has become slightly worse, because now I can hear the rattle at cold start idle and I notice the vibration through the steering wheel (column) a bit more too. Oh well, I'll know pretty soon if the engine mounts were the culprit(s).

The engine mounts seems crap on our cars. Mine wasn't completely toast but definitely bad when I had the RBs replaced at 38k miles, imo crazy that they don't hold up (much!) longer. Anyways, in this case lets cross fingers it indeed is bad mounts!

I've had Powerflex mounts in the car for 4-yrs, 30k kms, zero issues. These seem to be a permanent fix for our cars.

spammysammich wrote

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

The front of my oil pan got into either the front subframe or the steering rack when my mounts went (I forget which)

Talked to me through the steering wheel.

Redd wrote

I've had Powerflex mounts in the car for 4-yrs, 30k kms, zero issues. These seem to be a permanent fix for our cars.

I also have the PowerFlex engine mounts and they’ve been trouble free and have barely noticeable NVH. My wife hasn’t complained once since they were installed in 2018.

Redd wrote

I've had Powerflex mounts in the car for 4-yrs, 30k kms, zero issues. These seem to be a permanent fix for our cars.

Didn’t you add heat shields to your mounts as well? I’m shocked ours don’t have them. Even Subaru puts heat shields on their mounts.

spammysammich wrote

Didn’t you add heat shields to your mounts as well? I’m shocked ours don’t have them. Even Subaru puts heat shields on their mounts.

Would polyurethane benefit from that? I assume that's what the Powerflex are made of. Gotta look into these.

Redd wrote

I've had Powerflex mounts in the car for 4-yrs, 30k kms, zero issues. These seem to be a permanent fix for our cars.

Curious about your NVH experience with them.

Also are you guys running the Street or Black Series bushings? With or without stiffening pins?

spammysammich wrote

Didn’t you add heat shields to your mounts as well? I’m shocked ours don’t have them. Even Subaru puts heat shields on their mounts.

Great point because I believe the prior gen E46 3 series and the E46 M3 engine mounts also had heat shields... See image below.
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https://www.pelicanparts.com/BMW/techarticles/BMW-3-Series-E46/14-ENGINE-Engine_Mount_Replacement/14-ENGINE-Engine_Mount_Replacement.htm
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a5m wrote

Curious about your NVH experience with them.

Also are you guys running the Street or Black Series bushings? With or without stiffening pins?

Slight additional vibration felt thru the steering wheel at idle, same as with VT mounts. No additional NVH otherwise. I have the normal mount (Street?) and did not use the stiffening pins.

I have E46 mount heatshields and a DIY heat jacket around my PF mounts. I thought it would be a good precaution as our engine mounts are horribly close to the exhaust headers.

Honestly the things BMW chooses to cheap out on or omit from their cars is baffling. Heat shields for fluid filled rubber right next to a header…

Honestly this is very similar to the noise I was hearing in my car, only to discover that my exhaust was cut clean through on one side: Fun Exhaust Surprise

If you haven't yet, check to make sure everything is looking good with the exhaust.