[Si-M240i]

I have noticed recently that at idle I have a rattle. the moment any throttle is applied...even 100 rpm it goes straight away.

If I am in the car with the doors shut and windows up, I can't hear it.
If I open the door I can hear it.

Its a very light rattle, almost like a thin wire vibrating somewhere in the exhaust. and it even seems to resonate down the exhaust system as I can hear if through the exhaust if I am standing behind the car.

If I lift the bonnet, I cant hear it.

If I pt my head under the car on the drivers side, I can hear it plain as day.

I thought it was the heat shield on the undertray but its not that.

Could it be a CAT breaking ?

So, has anyone had this or know what it is ?

[oldbilly]

could be wastegate rattle!

[badgerbrock72]

thought that was only 335i or am i talking out my rear?

[Si-M240i]

I also thought the wastgate issue was the petrol cars too. I have been told the turbos on the diesel are almost indestructable.

Any other ideas?

[Bulo335i]

If it is while you are accelerating at low low revs, it could mean the cat breaking up as this happened to me.

[PowerCorrupts]

I've got a very similar problem too! No idea what it is tho..

[C.J]

Exhaust flap?

[Si-M240i]

CAT - I am not swaying this way as it is only at idle. the moment the revs move the tiniest amouth the rattle is gone rather than gets worse.

Exhaust flap.....definately a NO. I don't have one anymore as I replace mey exhaust

[Si-M240i]

Well I have an initial diagnosys, subject to the car going on the ramps to look properly in about 10 days time.

Apparently it the flexi joint on the downpie to the exhaust.

If it can;t be sorted by repositionaing it, they will order a new one in and fit it under warranty

[durandm]

Sorry to revive an old thread, but it sounds like I have a similar issue in my 2011 e92 335d. Was the flexi joint to blame and did a repositioning or replacement rectify things?
Cheers

[old grey steve]

We see a few with Flexi Joint failure at a guess and its a pure guess concentrate on that area the downside of course is the cost, the flexi's break up from the inside delaminate and over time you'll see soot traces around the pipe area where of course exhaust crap escapes

[Si-M240i]

the flex was to blame but as I have an after market exhaust they would not replace it under warrant as it hadn't "failed" as such. As it was not leaking or showing any signs of damage they were reluctant to order on in and have the warranty claim rejected. There was another fix done that eliminated it instead at my request and free of charge........they raised the idle speed for me from about 650 to 690rpm and I haven not had the rattle return in several month so far to date

[durandm]

Cheers for the responses guys.

How much would the replacement of flex cost? Also, at what point is warranty expired on the parts involved? I'm just under 28K miles, fully stock. Bringing it in tomorrow for a check. Sorry for all the Q's, hoping I won't be breaking the bank just before Christmas!

Mick

[badgerbrock72]

another thing to check at minimal cost and effort is the exhaust tips, they can and do get little stones trapped in between the pipe and the cover, mine did this when i first had it and the dealer finally identified a load of bits of little stones that resonated/rattled at a certain rpm...

worth a look mate.

Garry

[durandm]

Just a little update.

Took it into garage on Tuesday, found the exhaust had been vibrating against the chassis, causing the rattle. They were happy with the flexi. Quick adjustment to the exhaust position settled things about 90%...unfortunately seems it's either caused or unmasked another problem. Getting a God awful tinny/metallic rattle when idling/rolling in stop start traffic which improves a great deal (but doesn't disappear) when the car is put into neutral. It sounds like something moving around or loose but doesn't seem to be there at all times. They did an oil service and changed filters when they took a look at the exhaust, any chance it could be related to that?

Either way I'll probably bring it into them again to have another look, will have to outrule exhaust stones in the meantime (thanks for the tip)! Really starting to annoy me now, the car is starting to sound a lot like the old fiesta I learnt in years ago. 😰

[Sameen_619]

Did anyone find a solution to this. I seem to have discovered this rattle on my car this morning.

I notice the rattle at idle when stopped and in Drive. If i put it into Neutral the noise goes away (or maybe not as loud). As soon as i press the accelerator the noise goes away.

[rasa bmw]

probably the heat shiels a little loose,maybe over the one over the pro shaft