My 2014 E350 started making this knocking noise. I have done oil change checked all tensioners and belt. I am thinking its something in the valve train but I am unsure. If anyone can help me diagnose this before I tear into it that would be very helpful.


https://photos.google.com/share/AF1Q...lqNVBmMFlrWWZB

 

The E350 -2014 is a great car.
I've listened to your sound clip. Your V6 tap-tap-tap does sound unusual....

What mileage do you have now?

What maintenance parts replaced so far?

What engine oil did you use?

Have you connected a good scanner to read what engine computer has to report.


tap-tap: fuel pump camshaft lobes floppy chain tensioners : yes?

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Its flap cycle is the intake camshaft forces oil out of it then low oil pressure refills it. So this identifies a tensioner leak through seal or missing/bad C-valve.

The tap-tap cycle rate identifies how much oil pressure is available to oppose camshafts torque forces.


Brendon, you are right to believe noises are great clues to what parts are causing noises. These sofisticated cars are designed with built-in warnings to help us pay attention to their Dr. visits.

 

How long have you owned this vehicle?

 

It would be great to process that sound and separate the two main frequencies. At least I think there are two. Then, it should be obvious how it correlates to the integer numbers involved.

At 600 RPM --> 10 Rev/second of the crankshaft -> 5 rev/second on the camshaft, correct? The HP fuel pump goes with the camshaft speed, correct?

In that case, there should @5 tap-tap between two mississipi's

 

135k miles
As of right now I have not had to replace any parts. I did do the 100k service and did the transmission and spark plugs.
mobile 1 5-40 euro
I have not hooked up a scanner only because the is not a CEL light on.
It also does it when hot and cold not only on cold start if that helps.

 

[QUOTE=chassis;8827436]How long have you owned this vehicle?[/QUOT
About 4 years

 

Ok great!

The way you report tap-tap does not change with hot/cold make a pulley wobbling with an old belt possible instead of cam/chain related.

The tap-tap sounds a bit on the slow side for being a 300Rpm camshaft...
Is the long serpentine a better frequency match?

What do you guys think?


If you want to rule out the serpentine, disconnect it for a quick test while your engine is still cold.
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Pulled the belt. No change in the sound. I may need a stethoscope to pinpoint it but it sounds like it's under the driver valve cover.

 

A long screwdriver, a hose, a broom stick?

As usual, extremely careful when dealing with a running engine and sticking something around moving parts.

 

The noise does not sound unusual to me. When did it change, assuming it was not there since the beginning of your ownership?

 

For comparison, I just went out and started both cars, they have been sitting for more than 12 hours, and the recording started after turning them ON, and enough time to open the hood and set the light. That is, below operating temperature, but already idling.

https://www.youtube.com/shorts/TnutYfbi8iQ

https://www.youtube.com/shorts/s6P38wLADpc

I do not hear the tap-tap, and I am not saying those two are perfect either.

 

That sounds normal. And mine also sounds like that but also has a deeper knock/tap like sound about half the speed as everything else.

 

Here is a video of a M276 Turbo being dismantled. After the intake and turbo are out, the engine is basically the same as the NA.

I have set the video exactly when looking from the back of the engine, so driver's side is on the left. Something that rotates with the engine is the vacuum pump on the left. I am not referring to the crankcase breather on the right.

 

The first of your links sounds like the high pressure fuel pump noise. I had this on my S550 and I ordered two new pumps to replace them both. One of the pumps had worn a dimple i the end of the "lifter" that runs against the cam shaft with a roller. Forgot the name of this part, but as it had the extra backlash from wear it started to make this noise. I don't think there was anything wrong with the pumps, just the lifter that had worn.

It runs fine like this until the lifter bouncing around long enough breaks up the surface on the cam shaft and then you have a bit more expensive repair to do.

I highly recommend you check your high pressure fuel pumps/lifters out.

I assume here you have the DI engines.

 

Listening repeatedly I can hear something in the back. I will take a look at it. Thank you for pointing it out.

 

My 2¢ on M276 NA is it has only a single HPFP and no vacuum pump present unless turbo option.
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Sounds like you need to open things up for wear inspection.
We come full circle because as long as you open you may as well do the maintenance instead of 15000Mi later.

 

The valve train makes its normal noise but in your noise clip I hear this higher pitch noise that I had, and it definitely was cause by the fuel pump/lifter wear. I really think it was the lifter wear and the fix fore that is to replace the lifter (I don't r remember what the correct name for it is) only, not the fuel pump, but as I had the parts and I was there I replaces all of it.

Check it out before it ruins your cam shaft!!!

 

https://www.fcpeuro.com/products/mer...500122#fitment

I think you are referring to this part, correct?

 

If the suspect is the HP fuel pump and/or its roller lifter, and your engine is therefore the M276 direct injection, here is how we can narrow it :

01. Do a proper video recording ( don't move don't shake ) closest to Bank 1 ( Right side ) firewall, where the fuel pump is at, hoping we can get a good audio.
If an M276 3.5 NA , its camshaft fuel lobe is 3 lobes. See below :



This means for say 600 idling RPM, divided by 2 ( because camshaft is 1/2 speed of crankshaft ) and then multiply by 3 fuel lobes.
So 600 / 2 x 3 = 900 pumping events at 600 RPM idling. This we can catch its audio peaks if you record well and we can then verify, are we hearing a 900 RPM or 15hz audio peak ?
If we are, we have narrow down to HP fuel pump and/or its roller lifter.

That is why the audio recording need to have that tok-tok-tok sound clear enough for the audio section of the video editor to show their magnitude.

Based on M276 3.0 Turbo, but HP fuel pump position and overall this 3.0 is so similar to 3.5















However, based on your short recording of the tok-tok-tok sound, your issue is not with HP pump region, the frequency is too low .
Here is why I said so :














If you really want to get the tok-tok-tok sound frequency right, do a full 30 seconds video and set your camera to do 60FPS, resolution 1080p is enough.
You need to do a slow swipe to see where the highest noise is as RECORDED, and when you find it, use that location to do a full 30 seconds video recording.
Practice till you get the loudest tok-tok-tok sound and share with us.

Make a paper sicker ( masking tape ) label on your engine as shown below, divide it into 4 zones so you can later ID where the sound was loudest, when and if that
big black engine cover-intake air combo plastic get removed.





When I said practice, practice as a videographer, so that we can see by position where the loudest sound was.
What you see we can not see, we can only see the video you took. Use wide angle first and then slowly close in for closer view.
When showing someone by photo or video, one need first to do wide angle and then zoom in on the item/location.

Have fun recording...................

 

is dry shaft causing scorings?


Factory new roller...

Why is the roller having such a hardtime rolling... this correspond to the passenger side VVT Gear, the first one to go bad.
Looks like more oil would minimize frictions.
The HPFP is the last bearing surface ssrved by oil conduit that gets the least oil delivered. So it gets distressed prematurely by friction generated heat located at engine firewall.

If we provide better lubrication it will be an improvement
Like disable low-pressure solenoid and C-valve to prevent hydraulic raming.

The roller looks like a joint tune-up part with the 100kMi PCV-Refresh right next door

> TAP-TAP...:
You won't be wasting ressources with:
New passenger side tensioner and a new Check-Valve

You want to be... quick/cheap change only passenger side.Driver side chain is independently controlled.

If that doesn't bring joy then HPFP roller assessment
🤞

 

Its probably start of engine lube starvation Cali.
The HP pump is high point and is at the very back of the engine.
Simple scoring like that is no big deal as it is not compression work like piston/cylinder liner.
It can't be felt by touch or nail
Wait till u open up your HP fuel pump....

 

I am itching real bad to disable the oil pump solenoid either with vediamo massage or
with a bypass through dummy resistor (no code!) inside the ECU connector cover.

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It is easy. Get a suitable dummy load resistor and also use some sort of LED as visual.
I can dig up my files and tell you how many milliamps the switch is consuming, so that your DIY-Hack will not trigger any DTC at ECM
Look at your N3/10 wiring diagram, you probably have an X26 intermmediate connector too like my 3.0, hack it there and not at ECM connector

 

This will be my first time really tearing into a Mercedes. I am assuming by the tensioner you are talking about the timing chain tensioner not the serpentine?
What is the check valve your talking about. When I do a search many parts come up to do with oil check valve and a pcv check valve.