My 98 328is makes a high speed knocking sound after a good hard drive when its hot. The sound immediately goes away when you depress the clutch pedal and returns when you release it. The clutch is brand new and was replaced by BMW. The car was making the noise before the clutch install aswell.

Any ideas of what it could be?

could be problems with your DMF (Dual Mass Flywheel) I take it the noise is apparent when you are back from a run but stationary and idling , do you get a knocking noise when you kill the engine as well. If so I would definately be thinking DMF,

yikes, that would be expensive, although a good excuse to get a lightweight:)
yes, I hear it when the car is at idle after a good hard drive but I don't think it continues after the engine shuts off. I think the tech at BMW would have inspected the DMF when doing the clutch though so I dunno.

yikes, that would be expensive, although a good excuse to get a lightweight:)
yes, I hear it when the car is at idle after a good hard drive but I don't think it continues after the engine shuts off. I think the tech at BMW would have inspected the DMF when doing the clutch though so I dunno.

you may be suprized... most dealerships are flat rate... so I doubt he is going to take anymore time than is absolutly necessary to replace ur clutch... I am not saying he didnt expect it but it is most deffinetly a possiblity. Good luck with your car. I hope it works out for you.

yikes, that would be expensive, although a good excuse to get a lightweight
yes, I hear it when the car is at idle after a good hard drive but I don't think it continues after the engine shuts off. I think the tech at BMW would have inspected the DMF when doing the clutch though so I dunno.

Sometimes the DMF can sort of rattle/knock just at the point the engine stops
turning after turning it off, just a momentary knock/bang.
Unless its in warranty you could just live with it.