My '06 has a hard knocking noise in the front area underneath the car, especially in cold weather or cold start. It is more like a metal-to-metal rattle (but loud) than anything else, and does not exhibit itself at highway speeds, or after it's been driven 10-15 miles.

To solve, replaced the wheel hubs, struts and shocks with Bilstein PSS9, Alta front-end rear control arm bushings, etc., etc. It also has TSW engine damper and Brembo GT brakes in the front (the rotors have a little play between the hat and the disc, but that is the Brembo design). None seem to have caused or fixed the problem.

All nuts/bolts under the car have been checked; none are loose or missing. I am at a loss. The noise is annoying, but does not seem to affect steering and handling.

Any suggestions as to the root cause would be most welcome.

 

Not much to go by.

Does it happen when driving over bumps in the road ?

Does it happen when parked when engine is idling ?

Does the pitch of this noise vary with an increase in RMP's or road speed ?


All I can think of right now is maybe a bad crank pulley....upper engine mount ?

 

Did you check the front swaybar bushings?

 

GrayRaven and WayMotorWorks

Thanks for the suggestions. The noise is a hard metallic, as though someone left a big tool (e.g., large crescent wrench or air ratchet) in the engine compartment, but we cannot see anyting like that.

The front sway bar bushings are fine (no play or sign of deterioration).

The noise goes away after 15 or so miles of driving.

 

Well, the problem seems to have been caused by after-market positive steering response system. I had installed them about a year ago, and they made a significant improvement in steering response and handling. However, after 8-9 months, the damn noise came about, driving me nuts.

This week we replaced them with OE control arm bushings and housings, and the obnoxious knocking noise went away instantly. I do miss the precise steering response, though. Maybe they are best left for track-only cars?

Thanks to all those who provided insight earlier.

 

At least we had fun full day installing those suckers! Glad you found and fixed your noise problem.

Bryan

 

my 05 MCS maid the noise yesterday and today 14 feb2011 boom. ahhh smoke everywhere. mini said that that they have had a few come in with the loud noise because of low oil. mine was good. not sure but i told my wife to watch here oil level in here 09MCS for now on.