[Grohouse]

Hey guys,

So I've had this faint metallic rattling noise coming from what I think is the engine bay, perhaps underneath the car. I would describe the noise like a bolt/coin being knocked around gently in a metal compartment - but a bit deeper in tone.

The noise appears evident when I have the window down and accelerating relatively softly (ie. revving the crap out of the engine masks the noise, though I assume it's still there), otherwise with the windows up it's not noticeable.

I believe it may be 2 possibilities:

1. A Loose exhaust shield
2. Damaged Catalytic Converter

I'll have a look underneath the car this weekend to check for any evident rattle from the shields as its a simple job.

In the meantime, I was wondering if anyone on these forums has had a similar problem like this before. Some online research shows many people who display similar symptoms have needed to replace their catalytic converters as the honeycomb internal structure has broken.

Any help would be great!

[R32GOJIRA]

If you have a 335 with an n54 motor it may even be the start of waste gate rattle.

[CYL]

I am thinking while not all N54 suffers from rattle, does the extra boost/power from a tune stress the waste gate too much causing the waste gate parts loosen up and rattles?

[R32GOJIRA]

Originally Posted by CYL

I am thinking while not all N54 suffers from rattle, does the extra boost/power from a tune stress the waste gate too much causing the waste gate parts loosen up and rattles?

It would certainly speed the process up i would think.

[Brule]

Originally Posted by CYL

I am thinking while not all N54 suffers from rattle, does the extra boost/power from a tune stress the waste gate too much causing the waste gate parts loosen up and rattles?

No, but putting aftermarket down pipes increases the noise you can hear.

If your on 3psi or 30psi the flapper will still seat the same way and have the same wear in the housing.

[iliketurtl3s]

Hahahahaha this is the sound all n54 owners dread.

[Grohouse]

325i, no waste gate.

[Socket]

Originally Posted by Grohouse

325i, no waste gate.

He has you there lol

[R32GOJIRA]

Hmmmm 🤔

[EB89]

Did you change anything on your exhaust recently, if you did chances are something is loose, I had this and it was a loose support thing.

[Ken Oath]

Any codes? Injector 'ticking'?

[Grohouse]

It has been a while since I visited these forums. I haven't been chasing this noise up until now (the weather has been getting better and I tend to drive with the windows down, so I tend to hear it regularly again). I've stumbled across the following thread on Bimmerfest forum, where another owner reports to experience the same noise coming from his 3 series. His findings point to a loose/rattling heat shield on the passenger side near one of the engine mounts. I'll be taking a closer look next weekend and will report back if this is actually the cause.

http://www.bimmerfest.com/forums/sho...=716499&page=2

I'll also have a look at the exhaust as well to see if there are any shields/brackets lose.

No codes are being triggered, I don't believe it's the injectors - the rattling sound is only produced when in motion and appears to be audible at slow speeds (I believe its there at higher speeds, but I can't hear it over the engine/road noise).

[Mayuri Krab]

Originally Posted by iliketurtl3s

Hahahahaha this is the sound all n54 owners dread.

I fully embrace the noise, gives the car character

[Grohouse]

Fixed. Ended up being a bracket holding a green bush which connects the first section of exhaust piping from the engine to the chassis of the car. I installed a spring washer between the bracket and the car, this seems to have done the trick. Happy