New Noise - V12
 

I have a 2003 S600 (90K mi) that has developed a new noise. It is not present when engine is cold and developes only once it is warmed up. Changes directly with engine speed.

I have used the ear and screwdriver method to try and find the source to no avail.

Anyone identify the attached sound file.

https://drive.google.com/file/d/0B_Z...it?usp=sharing

Thanks for any help.

Take off the serpentine belt, inspect it, and fire up the motor with it off to see if the noise goes away. If it does check idler and tensiner pullies and see if you have a loose pulley somewhere else.

That sounds like sticky/knocking lifters to me...

Removed belt. Noise still present so not related to belt or any belt driven accessories.

No noise until engine warm. You cannot hear it in the car with windows closed - but this engine was super quiet till last week and my wife actually noticed it when I let her out of the car.

Does not sound "metallic" but more like an air diaphragm cycling (air pump). I removed lower engine covers to lister at lower side of engine block - no unusual sounds found. Removed air cleaner assemblies to access v-area - no noise maker found. (turbo inlets were both clean though)

So far I have put the "screwdriver ear" to just about everything on top and bottom of engine. Best guess is noise is from front drivers side quadrant. It actually sounds like it is coming from the front end of the driver side coil pack area to be specific.

Noise does not appear to be present under load (acceleration or cruising speed)

The noise started last week and I changed the oil over the weekend (was time) with no change in noise level. I'm going to hook up DAS this am and do some oil pressure checks versus temp / rpm.

I'll keep updating as I try other ideas.

Update: I decided to replace oil with higher viscosity (15w-50) for a test / clean. Using Rotella 15w-40 HD oil (I use it in my Duramax Pickup). I know this is not spec -- but it warmer outside and it will only be for a short duration (1000 mi). Still making same noise but I have not run it very long yet (I'll see if HD oil helps clean lifter?)

I have determined the noise is in time with the valve train by watching the cam/rockers under the oil cap as a reference.

I only had 200 miles on the Mobil 1 0w-40 from the change last week-- it came out much darker (black) than I expected. This was the first change since I have owned the car and about 7,500 miles since last change. I have the service records on the vehicle and it has been changed per Mercedes spec by dealership since new (from VMI history printout).

My SLK get changed once per year at about 5,000 miles and is still amber colored -- contrasting the S600 oil that was very dark in 200 miles. Looking in the oil cap on the valve cover and the oil filter chamber showed no sludge or deposits -- just much darker oil than I would expect.

Other than noise - engine runs perfectly - no codes, no misfires. You cannot hear the noise in the cabin - only outside by the hood. It is a new noise -- was not there earlier - so it is not normal.

Took a 600 mile trip last week -- oil looks much better - no real change in noise. I plan on an oil analysis after 1000mi to check for metal / other items as a data point.

Latest Status of Noise Saga:

Removed Head Cover (valve cover). - This took about 90 minutes - could do it faster second time. I found removing the intercooler totally was much easier than "folding it out of the way" as suggested by WIS.


Inspection Results:
no excess play noted - everything seemed in order
no sludge (relief) - was surprisingly clean - not what I expected based on initial oil change.

Running Test with Cover Removed:
Allowed engine to warm fully - no extra noises detected (problem disappeared)
All oiling systems appear to be flowing properly (makes a mess)

Very short video of running with cover off.
https://drive.google.com/file/d/0B_Z...it?usp=sharing

Reinstalled cover - paying paying special attention to proper torque of all bolts for cover and attachment to cover (going into Aluminum and Magnesium)

I also changed out the HD Rotella oil after 1000 miles and replaced with Mobil 0w-40 with new filter.

Results:
After test drive no extra noise (problem fixed) but I did not find an identifiable cause. I am guessing that a few of the head cover hold down bolts under the coil pack may have been loose -- they were very easy to remove. This may have allowed the cover to act as a drum ??.

Driving around town yesterday - still no noise!

Planning a longer 60 mile trip today reconfirm. Always before the noise would start as soon as the engine started warming up - within 5 minutes at idle.

Photo prior to running with cover off - oil shields not in place.

Did yours remain quiet? Mine has the same noise, and like you I cannot see anything wrong. Mine comes 5 minutes after starting, when the engine is cold its silent.

Noise has not returned since repair. No further issues with "odd" noises.

Regards,

Chuck

Thanks for the update. Much appreciated.

i have done my valve cover gaskets, so have had the covers off and on.

Looking through the oil filler cap, the noise is in time with the valve train.

It didn't change with an oil change/flush etc.

I am not too worried about the noise, just be nice to track it down.