[Stuiterbal]

I'm looking for N54 sound expertise. Since a few months, my 2008 335i N54 (stock) developed a low rumbling sound during low throttle on a warm engine.It typically comes and goes but it is clearly noticeable.

A recording:

View post on imgur.com

(mostly second half)

- The car/engine otherwise runs completely smooth and handles high boost/full throttle flawlessly
- 170k miles on the odometer
- My usual shop sees no codes on their generic scanner
- No shaking during acceleration so I assume that rules out the engine mounts
- Coils, index 12 injectors and plugs all relatively new (<2 years old)

[Stuiterbal]

bump

[jacraest]

is it more of a high pitched rumbling, like scratching, or a normal rumble grumble?

[Stuiterbal]

Originally Posted by jacraest

is it more of a high pitched rumbling, like scratching, or a normal rumble grumble?

Its a low noise. Its hard to tell, even from the video, but it definitely stands out in loudness over the normal 'smooth' engine noise you have in any situation.

I couldn't correlate it to any specific rpm level. Its not there when fully idle. I haven't tried putting it in neutral while in motion though.

[Stuiterbal]

I've now started noticing vibrations whilst stationary and also while revving hard. I'm now thinking that my engine mounts have started to fail. Guess I'll look into replacement.

[jacraest]

check under her or the mounts for leaking hydraulic fluid. E90 engine mounts have hydraulic fluid in them. When they fail, they'll leak. Otherwise it might be something else. Then again my door panel rattles when I idle, but I just put my leg against it and it stops.

[Stuiterbal]

Door panel rattling would drive me insane

I'll be having the mounts replaced tomorrow, I'll report back.

[Stuiterbal]

Replacing the engine mounts didn't really seem to fix my issues. One engine mount was leaking, the other could move around pretty freely so I guess both of them were broken.

The 335i has also been developing moderate vibration while idling. A generic scanner didn't pick up any errors but it may be misfires. My spark plugs are 30k miles old, maybe they need replacing. I'll take the car to a BMW specific shop sometime.

[Stuiterbal]

A bit of an anticlimactic ending.

After visiting several shops, it was determined that the vibrations originate from probably a faulty torque converter. Not from misfires or worn engine mounts.

Getting the labor for torque converter replacement done at a shop goes beyond what I'm willing to spend, giving the overall mileage and state of my E90. A week prior I actually just had the starter motor replaced, as I got stranded with a broken one.

As with the noise from my OP, I'll probably never know the cause, unfortunately. I'll set my eyes on a new daily driver.

[jacraest]

Megabummer. It really sucks when this kinda stuff happens, with fixes far too expensive. I replaced one of my rear hubs since new ones are $600 when I cross threaded a bolt. Seen way too many e90s in the junkyard for that very reason. Good thing you replaced those engine mounts though. Wish you the best of luck with your bimmer.

[jacraest]

took my bimmer to the shop to get my own scratchy scratchy noise fixed. Turned out to be a failed DISA valve covered under SULEV warranty.

[Stuiterbal]

Thanks for circling back on that. I wasn't aware of the DISA valve but it was good reading up about it