[R00tie]

Good afternoon Guys,

I’m owning a beautiful ’05 325i saloon. In holland we do have attractive taxes driving 15+ years old cars. Especially when driven for business. With that in mind I bought mine in Octobre 2018, so it’ll be a so-called ‘young-timer’ in 2020. So it is now... ��

It is really a fun driving car. Very responsive, nice sound and also the automatic gearbox does it’s job well.

It just passed the 200.000km’s and now i’m trying to solve a problem what’s been on my mind since I bought the car.

Often at acceleration when the car is driving ‘cold’ I hear a very worrying sound from the engine compartment. It’s there for few seconds on heavy load and/or acceleration. I can reproduce it often for several times. But when the engine is on good operating temperature, it doesn’t make this sound anymore.

I can describe the sound as ‘crackling’, perhaps ‘rattling’ and it’s pretty audible within the car itself.
I’ve mounted a gopro in the engine compartment and tried to evoke the weird sound; with succes. However only once. I’ve put in a video below (in the first take it’s audible):

Any idea what this might be? I do not think the sound is coming from the distribution chain, since it is not audible when starting the car. Only at load/acceleration. But ofcourse it could be. Can it be a misfire? Since the sound is pretty loud? Low fuel pressure? Some other component attached to the engine?

I’ve been running on unleaded 95 (with 10% ethanol). Now it’s running on unleaded 100+ RON (Shell V-power racing). But the problem is still present.
Does anyone know what this might be?

I can eassily drive the car to the south of france, without any problems. 1300+ km’s from my place. With peeds going up to maximum.

However the presence of this issue does not ease my mind

Details of the car:
Engine: N52B25
Just renewed the waterpump at 176.000 km’s.
Automatic gearbox (ZF): 6HP19
The engine uses 1 liter 0w30 per ~5000km's

[E92William]

Have you been able to scan it with a proper scantool? And by that I mean something that will show deep codes like disa valves and such. This is odd and codes would help guide towards some direction. One thing I would definitely do is have someone slightly rev it while you hear around under the hood to see if you can figure out where it's coming from.
Another thing could be take off the serpentine belt and see if it still makes that sound, if it doesn't then you already know to check pulleys and stuff but if so then it could be something in the intake or a piece of catalytic converters material flopping around. I doubt it's lethal to the engine or it would have had issues already

[R00tie]

Originally Posted by E92William

Have you been able to scan it with a proper scantool? And by that I mean something that will show deep codes like disa valves and such. This is odd and codes would help guide towards some direction. One thing I would definitely do is have someone slightly rev it while you hear around under the hood to see if you can figure out where it's coming from.
Another thing could be take off the serpentine belt and see if it still makes that sound, if it doesn't then you already know to check pulleys and stuff but if so then it could be something in the intake or a piece of catalytic converters material flopping around. I doubt it's lethal to the engine or it would have had issues already

Thanks William, for your detailed reply! I've been to an 'engine expert', and we've both listened closely to engine, while someone rev'ed up the engine. At that point the engine already was at operation temperature, and it appeared to function completely normal. No codes where found either, however i doubt if it was done with a proper tool able to scan the 'deep' codes as mentioned.

Usually it generates the sound only when it's cold and/or at the begnning of a trip. Accelerating towards a highway. After 10 to 15 minutes of driving it is not present anymore. The last days it's pretty sunny with nice temperatures in the netherlands, since the last post I haven't noticed the sound.

I will certainly take the car to a specialist for furhter analysis. In the meanwhile i keep recording the engine sounds. When noticed again, i'll update here

[R00tie]

I've captured an other video, in which the sound is audible multipe times.

The mic was installed above the intake manifold.

[E92William]

At this point I'd be almost sure this is some plastic bs flapping around in the intake system.

Look at your intake manifold and even though that's a 325i it could have one of these two disa valves. Look in between the intake runners in the middle and see if you see one and look above the throttle body on top of the intake and see if you see the other one. I showed some pics of a spare manifold I got.

These flaps tend to break off and flap around making a very similar noise to that.

IMO if it's not one of these flaps Then take everything off before the throttle body and check if there broken plastic stuff inside or flapping who knows. If not then it might be a piece of catalytic converter material flying around in the exhaust

[E92William]

These stupid little noises can get very expensive to diagnose if you're taking it to a mechanic

[R00tie]

Thanks again! I do have at least one DISA valve I guess. I made some pictues of it. I think this is no. 2:



And then this might be no. 1?:



I'll check on them first. I will take the car to a BMW specialist. However; I got all the tools and i'm pretty handy; But never worked on cars this way. Would it be a doable job to check on them?

What scan tool do you suggest for (deep) scanning the car?

PS. By seeing this pictures, it wouldn't be a bad idea to clean up the engine :')

[Tambohamilton]

INPA and a decent k+dcan cable...that'll give you everything you need.

[E92William]

Yep so you got disas. The one on top of the throttle body is easy to get out just 3 torx screws. Get it out and check the flap for excessive play.

[R00tie]

Update! It was indeed a failing DISA. As shown in the picture below:





The valve did come loose at the top of the bracket. Luckily it didn't break any further!

Replaced the part and did some other maintenance! The car is running smooooothly now Thanks for the help!

[E92William]

That's great news. Good it wasn't worse. Some stuff is easier than we like to think it could be to diagnose! Enjoy it

What you replaced is what I can see is the big Disa. You still got that small one in the other side of the manifold which maybe you can check next time if you get something like this or lack of power. I think it's very hard to take off without the manifold out.