Marius Daniel

Hi!
The engine om642 fitted on 350CDI Blue Efficiency produced in 2010, 90.000km, DPF equipped has an on and off ?metallic noise in the engine compartment, more intense at the back of the engine (~ Cylinder no 3, under the turbo)- noticeable at 00:40 in the attached video.
Fresh oil and filters rattle still there. Liqui Moly Top Tec 4200 5w30, MANN filter.
NO errors on tester, run well, normal fuel consumption, no metallic particle found in the oil filter.
What would it be the source of the sound, please!?
Thank you!

artim808

This sounds like a bad injector. Try to do injector leak test.

geniushanbiao

Be honest I feel the noise is normal for a diesel engine. If the fuel consumption is good and you don't see any injector leak (black death) then I would leave it the way it is. I have 2 OM642s both have similar noise but I might have mistaken. I guess it might be related to EGR clogging up the intake so cylinders are not receiving equal amount of intake air.

Marius Daniel

Thanks for your reply, artim808 and geniushanbiao!Update: it is not a normal noise for this type of engine, because it has recently appeared. Has a metallic on-and-off tone that is heard in the cabin now, it doesn't matter that the engine is hot or cold. Hopefully, one or more injectors are not working in normal parameters, I scheduled for the injector check on the bench test in two weeks.

I am still waiting for suggestions, please. Do you think it is an injector issue or something else?



New video uploaded (pay attention from 00:05, please)

Thank you all!

artim808

I still think it's an injector. I had similar noise until I replaced injector.
If you don't want to wait 2 weeks you can do injector leak test yourself. It is very easy. Just connect plastic tube to fuel return nipple on all injector, start the engine and watch which return line will have most fuel in it.
If you decide to do this test, put the fuel return hose to some bottle or somewhere, or you will have diesel all over.
Here is nice video how to do it:

Here is same test on OM642 engine:

geniushanbiao

Yeah you can do injector leak test yourself pretty easily like artim808 mentioned. If you go to youtube and search LegitStreetCars Alex has posted a video about this on his E320 CDI I remember I have watched it before. Same method except that he has the straight 6 OM648 instead of the V6 OM642.

Marius Daniel

Thank you all!
A quick update:Finally, I managed to do a leak test.

Left -injector no 1, Right injector no 6.





What do you think?



The engine still has an intermittent knock, is diffuse, hard to localise it. On auscultation with a mechanical stethoscope, the noise seems to be related to the injection system ( fuel pressure pump, both rails and metallic pipes from rails to injectors) and radiating to all engine compartment.

Car runs great, no errors stored in ECU, normal fuel consumption.

What test should I do next? Is it worth an injector cleaning on the bank at these values?

Thank you.

Alex Andru

Hi,
What was the issue in the end?

Thx!

Alex

Marius Daniel

Update:
The noise was way less intense during the warm season, perceptible (on-and-off) sometimes at idle or in light acceleration (NOT when a constant drive or decelerating ). It reappeared this winter when the environment temperatures drastically dropped. It is very annoying!!!.

Recently, I started the engine after a cold night ( -16Celsius ), the noise was very loud, so I listened to the whole engine compartment with the mechanical stethoscope.
My conclusion is that the noise is generated by the injection system. 100%!!!! as it can be heard very loudly on the ends of the injection ramps (around the sensor) and on the metal pipes that leave the high-pressure pump (see the red arrows).
Until the engine warmed up, it slightly emitted a white smoke or steam with a non-euro smell (likely burnt diesel). I also noticed a minor fuel leakage from the hose entering/exiting the high pump (due to metal contraction at very low temperatures) that stopped as soon as the engine warmed up (as did the smoke/steam). I mention that the noise of the injection system diminished as the engine warmed up, but did not completely disappear.


PS. The car runs great, no errors, normal fuel consumption, regularly serviced. Tried fuel additives - with no apparent results.


What may be the cause, please?
-The High-pressure pump
-The Fuel Rail Sensor (number 2 in the picture)
-One or more fuel injectors (due to blocked nozzles)?

What would you do next in the exposed case?
Thank you all for all the help you provided!

artim808

My guess is fuel injector. Fuel Rail Pressure Sensor doesn't make noise. The High-pressure pump can make noise, but it is slightly different. I believe the noise in your video is coming from fuel injector(s). Try top remove air filters and air intake pipe so you have good access to injectors and listen with stethoscope which one is troublemaker.

lorakw

Did you solve this problem?

Marius Daniel

Not yet, still working on it. Next week I will find more, I will update this post (good news, I hope!)

Alex Andru

Salut,

Ai gasit problema? Am si eu un tacanit din asta si ma dispera!

Mulțumesc!

Marius Daniel

Urmeaza sa inlocuiesc injectoarele.
Lasa-mi numarul tau de telefon intr-un mesaj privat

Resnais371

Hello, same problem here. Also listened for the noise with stethoscope- the noise frequency on the injectors seems to be a little different than the noise you hear simply standing in front of the car. The injector fuel correction quantities are no more than 0.2, which seem to be ok. I will try to replace the injector seals.

Misha_

I have similar noise and I think it is coming from that corner as well. I also have some exhaust smell. I ordered a new injector, should be here next week. I will update if it helps.

When testing, I tried isolating the injector by unplugging them on the right bank. When unplugging #2 and #3 the frequency of the noise was halved. My plan is to slowly replace injectors one by one anyway, so I will replace one of the two, and reseal the other.

Marius Daniel

Would be a good idea to check the Right exhaust manifold for leaks, as well:

Misha_

Thanks for the advice! I was going to retorque it too (recently installed), but idk how to go about testing it. I just tried the vacuum in the exhaust test yesterday, and could not hear any leaks in engine bay. Not sure that the pressure would get through the turbo though.... Have you replaced this yourself? I foresee it being quite annoying. The exhaust elbow from the turbo would have to come off for sure. And fitting it between the engine block and the pipe leading to DPF was a pain even without all the top stuff in the way....
maybe have the shield off, and spray some soapy water on the manifold while it is running...

Marius Daniel

I managed to record a video when the noise was audible. Using a Tester, I disconnected and reconnected the injector related to Cylinder1 several times as you can hear on the video.

At the latest diagnosis, injector 1 has the highest correction value: +0.58 mm3 / Hub (Injector 2: +0.24, Injector3: -0.14, Injector 4: -0.43, Injector5: -0.43, Injector6: +0.07)

My personal conclusion is that at least one of the injectors is decalibrated, clogged nozzles or has an internal mechanical problem. Or worst than this, the sound may be a rod knock or piston slap. I scheduled to replace all the injectors at a Benz Service in about a month time, but till then I want to hear your opinion, please.

So, what do you think, is it a sound caused by injectors or not?


(Repeated disconnection and reconnection of injector 1)

Marius Daniel

Misha_

Thanks for the update! What you hear is exactly what I heard when I disconnected 2 and 3 one at a time. I have my fingers crossed it is injector blowby. I do smell exhaust too, that is what gets my hopes up if you will.
i got my new injector yesterday. I have tomorrow off work and will install it and report back.

​​​​​​One thing that is weird in my case is that all my calibrations in first column (on the menu you screen capped)

show up as 0. I must need to reset something...

Marius Daniel

Misha, thanks for the reply.

Maybe your diagnostic tool is not reading the correction values.
Fingers crossed for tomorrow, I wish you solve the annoying problem.
(Fix new copper washer, new bolt, use ceramic grease and code the new injector in the ECU )

Misha_

I am using star diagnostic, so I think it should. I mean it gets the values at the two higher pressures.

​​​​​​Yes on coating, washers bolts and coding the new injector. Btw I will be trying thicker washer I found on rockauto. Much cheaper than the Honda ones people suggest. Will see how that works.

Thanks mate!

Marius Daniel

Misha, any news?

Marius Daniel

In my case, the noise has disappeared as the weather warms. I suspect one of the injectors, I will check & clean all 6 when the noise will reappear.