What could be this sound (attached)?

[Peter_Nik]

Dear All,

After purchase of my E200 (mopf, petrol, 24000km, after MB maintenance at 23500km) I recognized that its engine makes unexpected, IMHO, sound when it is cold. It sounds like metal knocking+a bit of yelping.

The sound disappears after warming up.

I don't remember that the sound appeared when the car was started up in the dealer's showroom at +17...+18C, but it is repeatable and recognizable around 0C.

What could this be? Its rate depends on the engine's rpm, but a few times less than the rpm.

You may find the sound attached in mp3 format. It was recorded inside my garage box this morning.

By the way, surprisingly I found that this higher frequency sound may not be heard on some PC players (cleaned by noise reduction???), but my phone and another PC definitely deliver it.

I would appreciate your opinion, but also I plan to visit MB dealer today afternoon.

Danke .

[Batterietester8329]

Where does the sound come from? Is it from a box near the ABS in your engine compartment? Then maybe it is the regeneration valve.

Für die Einheimischen: könnte es das Regenerationsventil sein?

[Peter_Nik]

Zitat:

@stoffel 05 schrieb am 9. Februar 2015 um 11:45:05 Uhr:

Where does the sound come from? Is it from a box near the ABS in your engine compartment? Then maybe it is the regeneration valve.

Für die Einheimischen: könnte es das Regenerationsventil sein?

I'll check this out and report here .

Thanks!

[Peter_Nik]

Zitat:

@stoffel 05 schrieb am 9. Februar 2015 um 11:45:05 Uhr:

Where does the sound come from? Is it from a box near the ABS in your engine compartment? Then maybe it is the regeneration valve.

Please find attached the image of the m274 engine with the red area indicating the place where the sound is coming from below.

Unfortunately I can't localize it better.

Thanks!

P.S. MB mechanic was not able to identify the noise by the recording and the warm engine did not make it too while I visited the MB dealer. We agreed that I bring my car to them for the overnight stay on Friday and they check it on the next morning.

[zoekie]

after heraing your soundfile i would say that this is a failure of the manifold. i remembered that sound of my opel omega v6 which had a demage on one side of manifold. the description was the same, when it was cold you can hear it, and after getting on temperature there was nothing. hopefully you will not have a demage, because the turbo is welded with manifold together on M274....

please revert what was the origin of the failure.

thx.

zoekie

[Peter_Nik]

Zitat:

@zoekie schrieb am 9. Februar 2015 um 22:10:14 Uhr:

after heraing your soundfile i would say that this is a failure of the manifold. i remembered that sound of my opel omega v6 which had a demage on one side of manifold. the description was the same, when it was cold you can hear it, and after getting on temperature there was nothing. hopefully you will not have a demage, because the turbo is welded with manifold together on M274....

please revert what was the origin of the failure.

thx.

zoekie

Danke!

I'll transfer this idea to the MB mechanic on Saturday.

But... is the manifold located below the side of the engine highlighted by red in the image in my posting above?

[Peter_Nik]

P.S. I'm not 100% sure, but it looks like the rate of this suspicious sound is 1/4 of the engine's rpm, i.e. when it is idle with about 1000 rpm (16-17 rounds per second) the sound appears about 4 times per second, i.e. could it be related to one of the cylinders?

[zoekie]

whats with your instrument cluster, did you get any warning ???? first of all i would ask your MB dealer, if he can read out the warning memory with his Star Diagnose System, but i think he will do this by his own, before getting started. IMHO i still think the failure is the manifold, if the cylinder will be demaged, you will not recognise any changing between low and high temperature of the engine....

zoekie

[Peter_Nik]

Zitat:

@zoekie schrieb am 10. Februar 2015 um 23:27:30 Uhr:

whats with your instrument cluster, did you get any warning ???? first of all i would ask your MB dealer, if he can read out the warning memory with his Star Diagnose System, but i think he will do this by his own, before getting started. IMHO i still think the failure is the manifold, if the cylinder will be demaged, you will not recognise any changing between low and high temperature of the engine....

zoekie

The car doesn't have any error messages on the dashboard.

By the way, the sound has changed with the temperature increase: the recorded one was taped at about -1...-2C, but today it was more like a belt's sound at +6C (almost no "knocking", but mostly "yelping").

Another update - I succeeded to better locate its source: it comes from the frontal part of the engine where the belt is located.

So I hope that this is the belt - but anyhow MB mechanic should find the cause on this Saturday .

Thank you very much for you help and discussion .

[Peter_Nik]

OK, my E200 was checked by MB mechanic this morning and also he looked up for this problem in the MB technical database.

1. The most probable cause is the generator's belt, the database contains similar issue (noise from the cold engine), and even the recorded noise presented in the database sounds close to the actual one from my car.

The solution is to replace the belt and check the generator's and other pulleys alignment.

2. The 2nd candidate is the turbine: it is known (from the db as well) that it may cause some noise in the cold state, but this should be fixed with the new software update for the engine, so it is planned too.

3. And also I asked to update the COMMAND's firmware (together with navigation maps) because I experience some "hiccups" with streaming music from my Android phone to the car audio system via Bluetooth.

This is planned for the coming Wednesday, so let's see how it works .

[Bruno_Pasalaki]

You checked the noise with removed belt? Whats with the injektors?

[Peter_Nik]

Zitat:

@Bruno_Pasalaki schrieb am 14. Februar 2015 um 11:23:37 Uhr:

You checked the noise with removed belt? Whats with the injektors?

The belt was not removed today, this is planned for the coming Wednesday.

[Bruno_Pasalaki]

Thats the first what you have to do. Remove the belt start engine and see if the noise is still there or not. When the noise gone you know there is something wrong with the alternator, waterpump or air condition. But i do not thing this come from this side.

[Peter_Nik]

Bruno, thank you for the advice and discussion.

Actually I still have about 6 months of the regular MB warranty and 2 years of the Young Star warranty, so I prefer to ask Daimler to fix this problem.

Their plan is to replace the generator's belt, so they do this and we'll see if the problem still exists after this or not.

I plan to bring an update about this on the coming Thursday if everything goes as anticipated.

[Peter_Nik]

Ok, I'm not sure is this post could be read by anyone at its new location as "MOTOR-TALK forum in English" does not look very popular .

But anyhow I'm reporting on the results" generator belt replacement + engine FW update solved the problem (tested @ two mornings).