An odd Rattle

[mo_s]

Hey guys, hope someone can help. Over the last few months there's been an odd rattle somewhere under the car but sounds like from the front. It sounds like mettally or a tin with small stones been shaken.
Usually happens if you press the accellerator down hard and let go. As the revs drop just before the idle it gets the rattle. It is to an extent inconsistent and does not happen all the time. Also if you ease the accellerator when letting it go it doesnt happen.

Its a 320d Auto, gave it to BMW a few times but still they can't find it or they say they can't hear it, murphy's law, so far theyv checked for loose covers under the car and have checked and retorqued the suspension and the exhaust brackets.

I'v tried reading about it and from what people say It can be the dual mass flywheel or a rattle off the wastegate. What do you guys think?

(cars going in again on wednesday for this and a leak on the gearbox sump)

Thanx guys, really appreciate any help raise: cos bm seem to only fix problems you find and can't figure anything out for themselves :nonono:

 

[mo_s]

anyone at all?...lol:fencelook:

 

[Twinz]

Gremlins? Eish cant help man...hope they find the problem.

 

[abmi0000]

Have you removed any of the covers as yet to check if anything has fallen in there?

Resonance can cause the rattle when you play with the fuel delivery.

 

[Ralf*]

Exhaust bracket cracked right near the main down pipe, just ahead of the Catalitic convertors, thats where mine had a very strange tin ratlle and also only as the engine achived idle, a touch on the accelerator and rattle was gone, as the revs come down to idle so the sound came back.

BMW coudn't source the noise, it took a local exhaust shop with a hose pipe in the ear method to find it....weld it and :thumbs::thumbs:

 

[mo_s]

Thanx Guys :ty:, cars still on mp atm. The first time I gave it in they checked for dirt and loose covers and never found a thing. 2nd time they just said they never found anything. 3rd time they checked shocks suspension and retorqued the suspension and any exhaust brackets. lol now the 4th time and I am wondering if they'l find anything. Generally If its not a blatant prob they never find anything :nonono:....thats why trying to get some info so as to point them in the right direction.....does it help if I say the easiest way t get the rattle is to put throttle and let go on an uphill?

 

[abmi0000]

Thanx Guys :ty:, cars still on mp atm. The first time I gave it in they checked for dirt and loose covers and never found a thing. 2nd time they just said they never found anything. 3rd time they checked shocks suspension and retorqued the suspension and any exhaust brackets. lol now the 4th time and I am wondering if they'l find anything. Generally If its not a blatant prob they never find anything :nonono:....thats why trying to get some info so as to point them in the right direction.....does it help if I say the easiest way t get the rattle is to put throttle and let go on an uphill?

Don't tell them.... Show them.