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· Registered
2 Posts
Discussion Starter · #1 · (Edited)
Car: E90 BMW. 2006 330xi 6 speed N52 engine.

Details. I have scoured all other old posts as well as other forums with no solution. Any insight or ideas would be appreciated. I am hearing a knocking sound coming from the front of the car, maybe the steering/suspension or engine compartment. I only hear the sound when the car is warm and I am driving at low speeds. As the car becomes warmer, the noise becomes more prevalent and even progressing from an occasional knock to a full on rattle. The noise mainly occurs when I am driving on an uneven road but start and stops will occasionally make the sound. I am having a tough time determining if it is a pop from a bushing or dense plastic banging against something. The noise happens both when the car is turning or driving straight ahead although the noise seems to be more noticeable when I am turning. The sound is not metallic. It is a knocking / quiet thud.

The below mentioned bad mechanic did not reattach the cabin filter and other plastic & electronic components that were removed when the struts were installed. I believe I have done my best to reattach all loose screws and clips, however some of the hardware mounts where broken during the job and I was forced to zip tie a few things to ensure they were secured. As ****ty of a job this guy did, I do not believe the cabin filter and surrounding plastic is the culprit. The most frustrating thing is the car drives perfectly. It feels great, the suspension is firm and responsive.

Work done in the last year or so (after noise started):

Work Done by a not so trusted mechanic

1. New front struts and mounts
2. New sway bar end links

Work done by a trusted mechanic

1. Lower Control Arms
2. New Starter.
3. New alternator.
4. Rear Diff fluid
5. 4 wheel alignment

Work Done by me

1. Front and rear brake pads
2. Front Rotors
3. Rebuilt front calipers
4. Inner and outer tie rods
5. Sway Bar Bushings

Other things I've checked which have not solved my noise problem:

1. Removed plastic engine cover.
2. Removed under engine plastic cover.
3. Placed thick carpet tape between a number of different plastic pieces within the engine bay (cabin filter, air filter, intake, etc.) in an attempt to silence two parts knocking into one and other.
4. Checked and rechecked tightness of all nuts, bolts, and screws in the steering, front suspensions, and other components within the engine bay.
5. Checked brake calipers for play and loose bolts.
6. I jammed cardboard under the hood and the hood jamb to ensure there was no rattle.
7. Valve cover and bolts are OK.
8. Sway bar is in good shape.
9. Noise occurs with or without brakes applied.

Things I have not yet attempted to try but are extremely time consuming and/or expensive:

1. Steering column & rack
2. Strut was over torqued during the installation damaging the strut or strut mount (can this be easily checked ***8211; everything looks secured and tightly in place.)
3. Sway bar end links possibly over torqued during installation.
4. Potentially other loose plastic.
5. Lower control arms (although they seem fine)
6. I've read some guys have had success replacing a "sheath" of some sort in the steering knuckle.
7. Look into possible loose drive shaft (I really think the sound is coming from the front).
8. Go through new suspension / steering components to ensure they are torqued to spec (god I don't want to have to do this)

· Tealeaf
18 Posts
Have you fixed it yet?

Presumably yr car has the headlight sprayers and to access those and the lights,
you have to take the front fender liners off, A fiddle as there are 2 different nut sizes
as well as a push/pull pin just to get them off.
Maybe it is the actual liner having some fastening missing or something behind them.

There is a lot of plastic up front anyway, between the kidneys and the rads.
Could also be something broken in there. I know as I got backed into by
a careless and just got it all replaced by their insurance.

Anyway, just a thought as I have the same car, but never yr symptoms.


· Registered
2 Posts
Discussion Starter · #3 ·

Thanks for the response. The headlight fluid sprayer was loose but was not the culprit.

The problem was a few bolts on the frame came loose resulting in the noises.

$150 from my local mechanic fixed it permanently.
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