[IrnBrulad]

So I've suddenly noticed a rumble on idle. Not a huge deal but the car's been smooth and near silent since I picked it up and this has started out of the blue. Just looking for ideas!

It goes away with a slight rise in revs so I'm assuming it's a vibration thing - more annoying than concerning but I like the fact the 335d was pretty much silent inside the car when it was started up

Hopefully video attached....


https://www.dropbox.com/s/woc5vy2dd7...%2002.mov?dl=0

[IrnBrulad]

Bump!

[330Stevie]

Can’t really hear this on the clip?

Is it constantly happening? If not the car could have been regenerating the dpf.
Alternatively it could be the air intake pipe into the air filter housing which can resonate, easily cured with felt tape.

[B1ue52]

Probably not, but get under the car and check your exhaust around the middle box/secondary Cat. I had the same issue at low revs, nothing at higher revs or when accelerating and was worse when inbetween gears like pulling away in second when you should be in first.

It progressed in to a tinny rattle, like a heat shield was loose or something, again, only at low revs.

It then progressed in to a knocking on the chassis cross member and a louder rumble.

The exhaust had totally rotted through (at 25k miles) at the join to the secondary Cat. The problem is that BMW don't hang exhausts all the down the car, only at the front and rear, so at idle, when the crack was open, then when accelerating and forces were on the exhaust through movement in the engine, it closed up, until it broke through so much it lost all structural integrity with no hangers to support it.

I got it TIG welded by a local custom exhaust place for £48.00 as I am out of warranty.

Worth checking. Just crawl underneath and when the engine is cool, push the middle box from side to side. If there is much movement you will see any cracks in the join.

Hope that helps you at least rule something out

[IrnBrulad]

Originally Posted by B1ue52

Probably not, but get under the car and check your exhaust around the middle box/secondary Cat. I had the same issue at low revs, nothing at higher revs or when accelerating and was worse when inbetween gears like pulling away in second when you should be in first.

It progressed in to a tinny rattle, like a heat shield was loose or something, again, only at low revs.

It then progressed in to a knocking on the chassis cross member and a louder rumble.

The exhaust had totally rotted through (at 25k miles) at the join to the secondary Cat. The problem is that BMW don't hang exhausts all the down the car, only at the front and rear, so at idle, when the crack was open, then when accelerating and forces were on the exhaust through movement in the engine, it closed up, until it broke through so much it lost all structural integrity with no hangers to support it.

I got it TIG welded by a local custom exhaust place for £48.00 as I am out of warranty.

Worth checking. Just crawl underneath and when the engine is cool, push the middle box from side to side. If there is much movement you will see any cracks in the join.

Hope that helps you at least rule something out

Cheers for that. Figured it was in the cabin - hadn't considered the exhaust. I'll have a look in case somethings lose. Hopefully not rotted after only 8k miles!

[IrnBrulad]

Originally Posted by 330Stevie

Can't really hear this on the clip?

Is it constantly happening? If not the car could have been regenerating the dpf.
Alternatively it could be the air intake pipe into the air filter housing which can resonate, easily cured with felt tape.

See I thought it was obvious! Shows you how differently people hear things.

Yep it's there all the time at idle. Or maybe I've just had the stereo down more these days and it's always been there?!? I'll pop the bonnet tomorrow and check the air intake pipe though. Cheers