Weird unknown sound, Intake rattle? - Video included!

[MMamazing]

Hi guys,

I have a weird rattle like sound on my M3 only under 40%+ load around 2600-3800RPMs. Sounds like a dull tapping sound. Only happens in 3rd to 6th gears under load. Cannot replicate in 1st or 2nd gear or in neutral (free reving)... Any ideas?

Initially i thought rod bearings, but recent rod bearing change did not make any affect at all.

Is this the famous intake resonance rattle/flutter? I've heard a few on youtube but did not expect the sound to be this loud and in this tone.. Something with the head? Bent valve? Piston slap? Knock?

Mods
Carbon Fiber Dinan Intake (Filter and elbow in stock airbox)
Akrapovic Evo exhaust system with 2 secondary HFC & resonators

Link to video
https://www.dropbox.com/s/ikyhlhfigk...03519.mp4?dl=0

https://www.dropbox.com/s/jmmw407s49...03855.mp4?dl=0

Any ideas? Any input is welcomed!

[///M Power-Belgium]

Originally Posted by MMamazing

Hi guys,

I have a weird rattle like sound on my M3 only under 40%+ load around 2600-3800RPMs. Sounds like a dull tapping sound. Only happens in 3rd to 6th gears under load. Cannot replicate in 1st or 2nd gear or in neutral (free reving)... Any ideas?

Initially i thought rod bearings, but recent rod bearing change did not make any affect at all.

Is this the famous intake resonance rattle/flutter? I've heard a few on youtube but did not expect the sound to be this loud and in this tone.. Something with the head? Bent valve? Piston slap? Knock?

Mods
Carbon Fiber Dinan Intake (Filter and elbow in stock airbox)
Akrapovic Evo exhaust system with 2 secondary HFC & resonators

Link to video
https://www.dropbox.com/s/ikyhlhfigk...03519.mp4?dl=0

https://www.dropbox.com/s/jmmw407s49...03855.mp4?dl=0

Any ideas? Any input is welcomed!

Your car sounds like an old tractor . I wouldn't drive it like that..
I heard a lot of S65 noises in the last years , but this I never heard before !
I would take it ASAP to my BMW/Dealer ..

On the other hand..It can be something with your exhaust , like exhaust pipe rattle (not sure)
Let us/me know...

[deansbimmer]

Doesn't sound like engine at all. Sounds to me like a loose trim panel rattling around. Probably comes up at a moderate degree of wind and road speed, which is why you can't replicate it standing still or in low gears.

Also, sounds like you've got some audible whine from a diff bushing or wheel bearing?

[JsL]

Doesn't sound normal.

Since you have an akra evo, check this thread too: http://www.m3post.com/forums/showthread.php?t=477144

[MMamazing]

Originally Posted by deansbimmer

Doesn't sound like engine at all. Sounds to me like a loose trim panel rattling around. Probably comes up at a moderate degree of wind and road speed, which is why you can't replicate it standing still or in low gears.

Also, sounds like you've got some audible whine from a diff bushing or wheel bearing?

Yes, the car has a solid differential bushings.. Also have some interior rattle sounds. Those sounds are normal I would love to think it is not engine related but the car seems to only make the sounds while under load though at a certain RPM range, suggesting something engine or motor movement related..

[deansbimmer]

Originally Posted by MMamazing

Yes, the car has a solid differential bushings.. Also have some interior rattle sounds. Those sounds are normal I would love to think it is not engine related but the car seems to only make the sounds while under load though at a certain RPM range, suggesting something engine or motor movement related..

Cool. The rattle and whine are explained. Otherwise, I hear nothing abnormal from the engine- it sounds healthy. If there is indeed something wrong with the engine then I can't hear it from your videos.

[MMamazing]

Thank you guys for the inputs so far, i appreciate it.

I hope that is the case deansbimmer deansbimmer

Also, i forgot to mention that the sounds seems to be comming from the left side of the front of engine bay. . .

I also ordered a replacement stock intake system to try when it gets here to hopefully eliminate some possibilites

[WingZeroX5]

You're also low on oil

[MMamazing]

Yes, good eye haha

[BPMSport]

Originally Posted by WingZeroX5

You're also low on oil

Don't forget the restraint system fault!

Those poor bearings

[DOCTOR.Y]

OP, can you repost the videos?