Here the update as promised: I first filled 7 liters Mobil 1 0W40 and started the engine.
At the beginning the noise was REALLY loud and it was coming directly from the oil pan (the car was on a lift). You could feel the vibrations in the oil pan. This was at idle. After increasing a little the engine speed the noise suddenly became much lower (?).
I let the oil temperature reach 80°C, stopped the engine end read the oil level from the dash, so I added oil until the level was ok.
Result: with Mobil 1 0W40 the engine is quiter (related to the oil pump noise) but the whine is not completely gone. Is it the viscosity? Some additive?

What could it be? I have the impression that some shockwave produced in the pump is hitting the oil pan that acts as a loudspeaker. The pick up pipe is going just straight to the oil pan. Is it possible?

i really wouldn't worry about it since 90% of all 55's make that noise. most people think it's the supercharger anyway

No supercharger, unfortunately it's just a plain 55
I went to 2 MB garages, one in Switzerland and one in Germany (I leave close to the border).
In Switzerland they told me they already changed the oil pump in 3 different cars without success and without really understanding where the noise is coming from.
In Germany they told me that if you fill something different than Mobil 1 something changes. They can't explain what is different and they did even open an engine to see if the parts were out of spec or worn. Nothing, absolutely nothing. They just know it can be oil related but nothing more. Otherwise, as you say, they say it can happen and it's normal.

Still don't like the noise...

Like i already told in post nr.26....
That noise we are hearing is engine oil pump noise (in 99% of 55k cars, especialy W211, which opil pump have 6 internal gears (compared to only 2 gears in all other 55k engine oil pumps). Also that engine oil pump noise heavily depends on oil viscosity we are using (and milage on that OCI).
After A LOT od researching on my engine, i have discovered that with German Castrol SLX Professional 0W-30 (in working temp it acts more like 0W-40) after cca 3000 km the noise goes down completely. Cold and hot engine.

I really don't think its the oil pump. Doesn't make sense with how quickly the noise comes on and how it runs at a constant sound then dies off in 3-4 seconds like an electric motor winding down.

Also, I have had my car make the noise a second time after some idling and driving a short distance to pull out of my parking garage at work. Idle's 3-4 min, drove a couple hundred feet and as I opened my window to put the key card in to open the gate so I can leave I heard it kick back in for a bit then wind down again.

It's not the oil pump unless there's an electric motor on it for extra cold start oiling or something silly.

We must be taking about two different noises because mine is NOT constant ( it's rpm related ) and after it calms down it never gets loud again until cool down.

With that said, Snogard has always said it's the oil pump, and he may be right, however my mothers C240 ( 2.6L V6 ) does the same noise. So does a co-workers E500. Those do not have the upgraded oil pump yet they whine just the same on cold start up.

I also hear it a LOT louder in the transmission bell housing than I do where the oil pump is. And it just so happens that the 722 tranny uses a gear pump for the transmission which is unconventional, and tend to be whiny, since most auto transmissions use vane pumps which tend to be quiet.

my engine always makes the whining noise at low rpms, doesnt matter if it's hot or cold. when i start off from a red light, it will whine up until about 2k rpm then get quiet. does it all day every day

Issue with pointing to a pump whether motor or trans is that the noise subsides within a few seconds of startup. Long before any fliud gets an opportunity to loosen/heat up.

Unless something is being drained and then filled up quickly which would make sense to me.

When I rebuilt my trans, no difference in noise whatsoever even though my original trans pump was shot it still made the same sound.

Gear oil pump in the trans? Is it losing prime and we are hearing it prime itself?

I have this noise (E55) and so did my mother-in-law (E350). Hers was tracked down to an A/C compressor. Mechanic put a smaller belt on the car to isolate pullies and this is what he got. Replaced compressor and noise is completely gone. Funny thing, mine sounds EXACTLY like hers did and another mechanic said mine is in the oilpan/internal engine. I tend do believe I may be getting BS from the guy who looked at mine. Will take mine to the first mechanic and see what he says.

A little update: I filled Castrol 0W30 and the noise became worst.
Can't tell if it was SLX but is was synthetic for sure. As I live in Switzerland we don't make a difference between German or other sources. But it may be what you're talking about.
After 2 weeks I filled Mobil 1 0W40 and the noise became less loud, but it's not gone away completely.

It is the oil pump for sure: I started the engine while on the lift and the noise was coming from a precise spot: the front part of the oil pan. I also checked other components as tranny and accessories: everything is quite.

Gear pumps aren't new to me as I install them in the company I work for (as for metering or transferring viscous liquids). When they are noisy sometime it helps to install a compensator, a pulsation damper.
Has anybody already tried something like that in those engines?
It shouldn't be complicated as around the oil filter housing there are several connector that can be used.

Stefano

I have wondered what the air hoses that go into the nose of the supercharger are for.

Is that some kind of EGR or is it part of the air injection system?

The passages look as if they wrap around the nose like it is an air pump built into the nose of the drive.

What is all of that for?

G

I removed all this. It's all part of the SAI system.

SAI??

Please help my with that one.

Thanks!


G

Secondary Air Injection.

Is there an air pump built into the nose of the supercharger?

If not what is the purpose of the passages?

G

No, the air pump is in the bumper near the airmatic pump ( drivers side ). The air pump has a hose that goes into the supercharger snout and the snout has passages that divide this air into the ports when the combi valves attach to. It divides one entry port into two outlet ports.

I still wanna knkw why my car makes the noise a second time when started and left idling for the most part. Doesn't make any sense if its the oil pump.

Sure sounds like an electric motor to me. Gonna try to make a youtube video of it.

You may be hearing the secondary air injection pump. It turns on every so often at idle or light throttle.

Does it run with what seems like every cold start? Soon as I fire it up I hear it kick in and run for like 30 seconds or a minute or two then you hear it turn off and slow down as the sound goes away over maybe 3-4 seconds. That's what I thought this was all about?

Very loud compared to everything else going on when I start my car. Sounds just like an electric motor starting up and slowing down when it turns off.

I changed the oil for the first time this weekend in my 05 E55. The PO had it serviced at the dealership for the first 7 years and 18,000 miles and I have no idea what oil they used but I put in Mobil 1 0w - 40w. 8 qts and the computer said that it is full. I drained the oil through the drain plugs and used a Mann filter. The car has always had a whine at startup but it would go away pretty quickly. After the oil change the whine is much more noticeable and it never goes away. After reading this thread I feel pretty convinced that it's the oil pump that I'm hearing and that it is related to the type of oil I'm using. I may add another 1/2 qt. and see if it helps but at least I know I'm not getting ready to lose a supercharger. Thanks to you guys.

Now if I could just figure out why the radio won't hold the station when I turn the car off and the navigation shows me 50 miles away. Just changed the auxiliary battery btw and no improvement.

Yeah, I think it may be the oil pump as well. I have tried all kinds of oils though and the noise stays the same.

Had the same concern about the same sound with my E55 and the dealer took every belt off basically and isolated it to the oil pump. A $1,500ish replacement to fix noise, so I think it'll be noisy for a bit.

For reference, those with a STAR system can disable SAI completely:

https://mbworld.org/forums/w211-amg/...rough-sds.html

I hear a loud whine when accelerating (much louder than normal) and eventually the car goes to limp mode. This whine sound different than the one you guys are talking about. Its very high pitched. Someone told me the conductor plate needs to be replaced and another person said the noise is coming from the transmission pump. I'm having the conductor plate changed Monday. Has anyone else experienced this problem or symptoms to these codes listed above?