I have an 05 mini s with 150k, keep up with all regular maintenance. While at a red light today I noticed a loud knocking sound, or louder than normal. After I got the car home I sat in it for a few min at idle, she sounded normal. Any idea at all what this might be. I recently got my seat recall done and while talking with the mini mechanic I asked him about the timing chain tensioner. He said on 05s he has never see one that needs replaced.

 

Is the car a manual? Probably clutch chatter, which isn't uncommon.

Is there oil in the car? A timing chain is more of a clattery racket than a solid knocking.

 

Throw out bearing rattle ? Can you hear it in front on the driver side.

 

If the sound goes away when you press the clutch in, It's your dual-mass flywheel. That can be intermittent. With the car idling and out of gear, depress and release the clutch pedal. If it goes away and comes back that's your issue. Depending on the condition of your clutch components, it may be best just to ignore the sound, since it's expensive to fix.

 

Check your oil level and if the noise comes back first thing I'd do is determine where the knock is coming from.

 

On my '03 R53 I had a loud knocking sound and it turmed out to be the sound made by improperly torqued loose spark plugs that had unscrewed themselves over time. I found out when one of them was blown out of the cylinder head taking 2/3 of the threads in the head with it. A Time Sert fixed it and I torqued all the new spark plugs to the proper torque (22 foot lbs if I remember correctly). Knocking sound went away after that.

 

Spark plug torque is 27Nm (20 ft-lb).

 

The sound went away when I pressed the gas only not the clutch. I will give my spark plugs a look.

 

Let me know what you find, loose spark plugs can cause a miss or noise. Check them out asap.