BMW 320d Engine Noises: Listen & Diagnose (MP3)

We've discussed this issue a few times: I'm noticing a strange rattling/metallic clicking sound in my car, especially at low speeds and under light load. It only occurs when I apply 'some' gas; it disappears completely when I press the accelerator harder or release the gas pedal entirely.

I created a website for that, and I put it there.

MP3 files for listening

It's been set up, and there are several 30-second clips. Maybe someone can listen to them and offer their opinion.

Perhaps the text on the page is actually useful; please check it.

Thank you very much in advance.
To everyone who is helping me calm my anxiety.

Best regards,
Jens.

Hi,

I'm familiar with a similar noise under the same conditions from an old Audi 80 1.3 gasoline car, manufactured in '73, that belonged to a friend. It had a connecting rod bearing problem. Contrary to popular belief, this type of damage is supposed to sound more muffled, but this engine ticked relatively loudly under constant load. When accelerating or decelerating, it was almost impossible to hear. He continued driving normally for quite some time, and about 10,000 km later, the connecting rod broke through its newly created opening .

Despite the usual background noise, it could also be related to fuel injection or piston slap due to wear. The latter is more likely if the noise is louder when the engine is cold.

Are there any other issues with the driving performance that you've noticed (e.g., excessive smoke, poor cold starting, jerky acceleration)?
Has compression ever been measured?

Oh dear...
How do I proceed from here? He still has one month of Euro+ warranty, but if I show BMW this noise... I think they'll say it's 'normal.' After all, it's quite quiet; the only reason I could hear it was because I recorded it in the engine compartment.

Otherwise, there's nothing really wrong with it. It starts up perfectly, doesn't make any unusual noises, and has no measurable oil consumption. I haven't had to top up the oil at all in 15,000 km.

hello jcee,
I once listened to how your engine sounds – it's quite a sound!
Try to pinpoint the source of the noise as precisely as possible, ideally using a stethoscope. If you don't have one, a screwdriver with a wooden handle might work; this way, you can use a process of elimination to rule out the crank mechanism or the valve train as the cause.
What is your oil pressure at 2000 RPM, and what is the oil pressure when the noise occurs?
I would probably rule out a piston pump, as it tends to tip over when the gas is applied. Unfortunately, I'm not familiar with your engine, but it has happened that the shaft wears out in engines with rocker arms.
Please check this and I wish you good luck; hopefully it's just a minor issue.
Hi Bastianna,

Update:
So, the reason the noises are so loud is probably because the hood is closed and the microphone is positioned directly above the engine. I'll try measuring it 'normally' with the hood open or from outside sometime this week. Apparently, everyone says it doesn't sound that rough when measured that way.

Ich hab dann mit einem langen Stab mal den Motor 'abgehört'. Result:
When I listen near the cylinder head or valve cover, I hear a consistent sound.
But directly at the nozzles (on the threaded nut), it sounds like a very loud hammering, which was quite unsettling.
However, I can't really judge it. The last cylinder is making a noticeably louder noise.
Then I thought I could temporarily disable the fuel injection for the cylinder by loosening the fitting nut. However, unfortunately, so much diesel leaks out that I couldn't keep it up for long. Does anyone have a tip?
I expected the sound/nail to be gone... but it wasn't. At least not in the last cylinder. Then I tried another one, and there was still no significant change in the metallic noise.
Shouldn't it change?

What's also quite interesting is that it seems there really is something to do with the exhaust: When I removed the metal plate for the fresh air intake into the interior ventilation system, located above the engine, I noticed that it was completely covered in soot from below.
'Besides the unpleasant smell that I always notice after being stuck in traffic for a long time with the engine running, the windshield often has a very slight film on the inside. I don't smoke, but it seems like my car does.'
It's all so cramped and packed together; how am I supposed to get past or reach that? It seems like something is definitely broken.

Even though you might think you've almost found the error, here's another suggestion based on my own experience.

I listened to all the sounds every 5 seconds and find it quite metallic. I also experienced a similar clattering or rattling sound, however you want to describe it, at certain engine speeds, just like you did.

I couldn't figure out what it was for ages, and you should know that this was very worrying. However, I occasionally noticed when looking under the eye area that the metal clips holding the exhaust bracket had become slightly loose, and now they were happily rattling and making noise at certain low engine speeds.

I took them out and, with a great deal of effort, reassembled them so that they no longer rattled.

Best regards, BigB.

Hello, since this seems to be where the most knowledgeable people are, I wanted to ask again/give an update, because that's all I have.

Everything as described above. The car just came from the workshop where the following parts were replaced: ZMS (flywheel), clutch, pre-catalytic converter, and one fuel injector (the one with the needle movement sensor).

My rattling/rattling noise hasn't gotten any better, and it's significantly louder (subjectively 5 times louder) when the engine is cold than when it's warm. I suspect that the workshop only assessed the noise after the engine had warmed up!

These noises barely let me sleep at night... What on earth is that?!
Despite the replaced injector nozzle, nothing has changed overall in the engine noise; they only told me that one was defective and also injecting fuel much too early, etc...

The noise still occurs, as described, at low engine speeds (i.e., low load) and in the low partial-load range around/above 2000 RPM (=low load). When it is accelerated more strongly, it disappears (or does it just become masked? hmm... I don't think so...). When the throttle is released (=thrust cut), it also disappears.

Therefore, it is possible to 'dose' around the area of constant speed.} You really need to pinpoint this specific range.

It sounds metallic, rattling/buzzing, perhaps also clacking/hammering. It could be the fuel injector, which is making a very different sound, or something else is vibrating.

That's my main concern; how can I further pinpoint the issue? The problem is that it's very difficult to reproduce in a controlled environment, which makes it correspondingly hard to track down.

Using the stethoscope method, I'm actually only hearing a very hard, metallic, hammering sound near the injectors/injection lines. AND perhaps also at the last cylinder (I'm hearing it near the valve cover screws). It sounds like small hammers hitting an anvil. Is this normal due to the injection cycles, or am I hearing a bearing issue?

To describe the sound again in words...

Here are the zones (assuming 2nd gear, >2000 RPM).
1. Idle.
2. Throttle cutoff.
3. Injection start.
4. Gentle acceleration.
5. strong acceleration.

Zone: I---1.---------------2.--------------3.------4.---------------------5.--I
Accelerator pedal: 0% 20% 23% >40%
Sound: tack/tack... (nothing) <--*a---< > *b-------

b) Normal typing: 'brrrrrrr' or 'drdrdrdrdrdr'
a) 'rerererererere' (meaning: brighter, clearer, more metallic).


I'm at my wit's end; how can I narrow it down further? I'm even thinking about building a contact microphone to attach to various points on the engine during operation and record the sounds, in order to pinpoint the source.


My key questions:

1) Why is it only occurring within this small area, and seems to disappear completely above it? (Hypothesis: There's play/looseness in the bearing/shaft, causing it to swing.)
2) How can I be sure that it's *really* just a story about injection (drugs)?
3) Other vehicles (unfortunately, only later models with CR instead of VP44) do not exhibit this noise.
4) It is SIGNIFICANTLY HIGHER for the first 10 km / 10 minutes. With a warmed-up engine, it's approximately 5 units smaller.


Any advice is welcome.

It's difficult for me to demonstrate the issue to the workshop because the car will be warm by the time I get there. Also, the workshop is 60km away, and I'm not sure if they heard the noise correctly the last time I brought the car in.

Perhaps there's an expert in engines or diesel technology located near Wilhelmshaven, Oldenburg, or Emden who can help?

Hmm, well, I think the engine sounds perfectly normal. But I'm not entirely comfortable with the 10W-60 oil; does BMW even allow that for this engine?

The initial injection is slightly higher when the engine is cold, which is why the engine sounds a bit different than usual.

My tip:
Remove the fuel injectors and have them rebuilt/inspected by Bosch.

Hello, thank you.
Then my car probably doesn't have such a big problem, but I do...: I guess I need to slowly start believing that it's normal. I've always been irritated that this rattling/metallic clacking sound is extremely noticeable at a specific pedal position when driving at a constant speed – meaning in relatively unloaded operation – and isn't present underneath or when pressing down.

Regarding the nozzles, yes, I would be interested. But the last price I got from Bosch was approximately €120 (+/- €20) PER nozzle, which already totals €360. (ONE has just been replaced by BMW ).

Are you aware of any other conditions? I've heard there's a repair kit available, and that it involves replacing the entire internal mechanism plus the nozzle tip, after which the nozzle is re-adjusted (balanced?).

Regards,
Jens.

... the flexible pipe was also faulty, which likely contributed to some of the noise heard in the recording.
I've made some improvements to it. Would you like to hear it again? I can send it to you by email, or upload it to my page sometime this week.

The 10W-60 is approved according to the 'ACEA' standard... (what does that stand for?).
Anyway, I had 0W-40 oil in it before (and it used half a liter less).

I'm still experiencing the issue where, after being stationary for a longer period (more than 1 hour), it takes 3-4 seconds for the oil pressure to build up after starting the engine.
How long does the oil lamp shine?
2. Does it rattle very loudly while it's running (=> hydraulic chain tensioner)?

I have learned from various sources that others are experiencing the same issue, but so far, no one has been able to identify a solution. It seems that somehow the oil filter housing or other channels are emptying, and the pump needs to refill them first...

I thought I was doing something good by using 10W-60 oil (Did I think wrong?!?!)
1. Does it adhere better to metallic surfaces?
2. It seems to have more reserve power, which might positively affect the lifespan of the battery.

Result:
The oil pressure warning light is still on for 3-4 seconds (it goes off immediately after restarting).
2. Higher fuel consumption (due to a lot of short trips!).
3. The rattling at the beginning is much quieter .

Maybe I'll use 5W-40 next time.

They checked the oil pressure last week, and everything was fine. However, that was with the thicker oil. They should have had comparable readings using the thinner oil.