Exhaust noise on start up

[Nev]

Hi folks,

Hoping for a friendly steer on this one. Just purchased a 2017 520d M-Sport touring. Almost every time I start it, after a few seconds there is a louder high pitched rumbling noise coming from the exhaust. It lasts for about 5 - 10 seconds and the stops and it does happen occasionally after that but never when driving on a long run. This is happening daily. I have attached a video which I took a few seconds after I pushed ignition from cold one morning. The car drives great but this is annoying and not something I ever experienced with a 2015 520d I owned up to a few years ago. I have it booked into a local garage next week.

[Greydog]

Hi Neville

Sounds as though something is loose in the exhaust a baffle may be

Hope the garage can sort it 

Dave

[Nev]

Thanks, just thought it odd that it only lasts for a a few seconds at a time, hopefully the garage can resolve and nothing too serious. I did see a topic from a few years ago pointing towards DPF regens but no-one seemed to find a solution to those noise issues.

[Greydog]

Morning Neville

When a Regen is occurring the engine has to have reached a high operating temp so doubtful at start up

Dave

[Nev]

Thanks again

[Nev]

Folks, this turned out to be the compressor starting up as there is an issue with the air suspension.

[Greydog]

All fixed now ?

[Nev]

Booked in early Jan under warranty so fingers crossed, compressor and two bags required apparently. 

[Nev]

Warranty garage having great difficulty finding any 'damaged' part or air leak so therefore I may have a fight on my hands to get anything replaced under warranty.