'Thudding' under the bonnet of my E91 330D

[AlmostUseful]

It's never really bothered me much as I never knew how loud it was (good sound proofing see) but I was outside the car the other day when it was idling and there's a really rhythmic thudding going on somewhere - I've googled it but can't see anything likely/common and wonder if any of you had experienced similar.

I've never given it much mind because it's never given me a s off if it going wrong, and it's had 2 or 3 MOTs and services where I presume (rightly or wrongly) that if it was something major and an opportunity to get more business the garage would have mentioned it. But now I'm thinking of selling it I thought it might put a buyer off so figured it is time to sort it.

Any possible ideas? It will go to a garage eventually, but being a child of the Internet generation I have some ingrained need to have a load of strangers identify it!

[AlmostUseful]

Just to assist you all, I'll try to post a YouTube clip or something with the engine idling so you can have a more educated stab, until then, just guess!!

It's quite bassy.

[vanordinaire]

I think the clue is in the 'D' at the end of the 330 on the bootlid.

[AlmostUseful]

Ha ha, I'm not much of a 'lol' kind of guy but it works perfectly there. Lol. (I can't believe I've done that I sort of public...)

Ok, over and above the clatter, there's a also a bass thud which sounds like I'm a bellend (well, I am, but for entirely different reasons!) with loud music when In fact my only crime is buying a car that's too small and runs on the juice of the devil!

[cerb4.5lee]

vanordinaire said:

I think the clue is in the 'D' at the end of the 330 on the bootlid.

[darrenw]

My Dad has a 2005 525d and that does it, we've wondered about it a couple of times. He's had it five years and it has always been there, never got any worse or anything so we've just assumed it's nothing to worry about.

[Swoxy]

Remove the engine cover.

[AlmostUseful]

darrenw said:

My Dad has a 2005 525d and that does it, we've wondered about it a couple of times. He's had it five years and it has always been there, never got any worse or anything so we've just assumed it's nothing to worry about.

Whilst owning it I've had the exact same thought, I just don't expect a potential buyer to believe "yeah mate, been like it all through my 4 years of ownership, nothing to worry about" so I'd rather get it sorted.

Swoxy said:

Remove the engine cover.

Will that make the noise more obvious or make it go away?

[mybrainhurts]

You might have a wildebeest trapped in the engine bay. Hope not, they're a bugger to get out.

[AlmostUseful]

I'm not sure there's room for one in there, what with the engine cover and that strut brace at the back of the bay, maybe it's just a small one? How big is a small wildebeest?

[AlmostUseful]

Righto, here's the video.
With the bonnet up it sounds more like air movement than any sort of impact.

The car runs fine, what part of thing could be losing air and not really be a problem?

Will try to get time to take the engine cover off tomorrow.

http://s222.photobucket.com/user/pimpingimp/media/...

[mybrainhurts]

AlmostUseful said:

I'm not sure there's room for one in there, what with the engine cover and that strut brace at the back of the bay, maybe it's just a small one? How big is a small wildebeest?

It's a bit smaller than a big one.

[mybrainhurts]

AlmostUseful said:

Righto, here's the video.
With the bonnet up it sounds more like air movement than any sort of impact.

The car runs fine, what part of thing could be losing air and not really be a problem?

Will try to get time to take the engine cover off tomorrow.

http://s222.photobucket.com/user/pimpingimp/media/...

Blimey. I reckon you've got a farting hedgehog, with a musical bent, in there. Amazing...

[AlmostUseful]

His rhythm is frigging insane, little bd must have a metronome in there. st, he might even have a proper gnome in there too!

[Osinjak]

That sounds like someone making a fart noise with the hand in an armpit trick. Not right though, that's for sure.

[wel7on]

Sounds familiar, in fact here is a thread I posted a few years back !!!

http://www.pistonheads.com/gassing/topic.asp?t=128...

It was the EGR.

Hope it helps

[MattOz]

Might be the pressure converter? Fairly common issue. Can sound like a thud, or even a duck quack. Seems to fit the bill!

[AlmostUseful]

Duck quack is a very good comparison when up close with the bonnet up!

[f1nn]

Jesus, the E90 330D I ran for the last 25K never made a noise like that.....it's sounds like a steam train getting going!

[AlmostUseful]

Well I'm about 75k miles into my ownership now and I'm sure it didn't always makes that noise!