bloohorseshoo

I have a 2008 S550 4matic P3 with 33k miles

There is a noise coming from the engine, in the back section of the engine compartment. It is hard to describe the sound, but it sounds like light tapping- like a compressor or a pump is working a little too hard, or is clogged. I can hear it clearly with the hood up, or from inside the cabin, in D and R and N when idle or driving slowly. I have read similar threads that describe a tapping noise from a faulty tandem pump for the Active Body Control. This sounds very similar, but this car does not have ABC.

The noise speeds up and slows down, occasionally stopping completely, but it has nothing to do with the RPMs of the engine, it is completely independent. It also has nothing to do with the AC/Heat, or driving over bumps, as some others threads have described.

I have taken the car to MB twice so far to diagnose the problem. Everyone who looked at the car heard the noise but could not figure out where it was coming from. They brought in an “Engineer” who promptly misdiagnosed the problem, fixing something to do with the AC Fan. They would have noticed it was not fixed if they test drove the car after, which they didn’t

The car is under warranty so they have little incentive to diagnose the problem.

Looking for some ideas before I bring it back to MB for the third time……ugh

THANKS IN ADVANCE for any help with this issue

J

RGS

I have 2007 4-matic with same noise. Local MBZ service says it is the purge valve on the air suspension and no way to fix---since it's at 0 speed, I just ignore.......
BobSpen

MBS430

it's a shot in the dark but try have them look at the fuel line damper.

a friend's S550 had the light tap-tap noise from behind the steering wheel and it got fixed with replacing fuel line damper.

good luck and keep up posted!

Atcpup

I had the exact same noise/knock you describe. Mine turned out to be the purge valve on the fuel evaporation system. They also added felt strips to the line retaining clamps. The part number for the valve is 000-470-88-93. You can google it to take a look at it. Completely got rid of my knocking.

kld36

good luck and keep up posted!

new550

I have same issue on 2007 s550 4matic....If this works for you Atcpup, I will likely have to replace mine as well...let us know if it works.

Anyone know if this can be an easy DYI replacement?

bloohorseshoo

Thanks for the input! Fuel line damper and purge valve have not been checked yet, so I am suggesting that to the dealer.

I am dropping the car off at MB this week.....Any other ideas before I take it in?

Thanks

J

cool_lagoon

bloo where you able to resolve the issue? this noise is inherent with all 221 series 2007 to 2009, still wondering if this can be fixed,

bloohorseshoo

And the verdict is.....Purge Valve

I had a test drive with the head tech at MB, he immediately recognized the sound. They brought the car in for the day at added felt stripping to dampen the knocking/tapping. I have the car back now and it is slightly better.

He and the head service guy acknowledged that the purge valve is an issue on this and a few other models from 2007-2009. Although it is a known issue, its not a part that is failing just a noisey one. The purge valve is part of the American emissions requirements and I guess the newer models are quieter.

Bottom line, the tapping noise is "normal" and I can live with it. Grateful was not something worse, as I had feared

J

Atcpup

I wouldn't settle for "normal" especially if its under warranty. To me the noise sounded like bad lifters(I know, old school stuff). It was a bit of an embarrassing noise to me before I had my purge valve replaced. Car is whisper quiet again.

VOKS7780

Sorry to bring back such an old thread but I think I need to change my purge valve as well but I don't know where to find it on the car. I have a 2008 S550. Any help will be appreciated. I already have the part number "000-470-88-93 PURGE VALVE"
"

marthyh

I too have this tapping noise at idle ,probably coming from this valve ,any info on its location would be welcome.

Have also read that its possible to disconnect it without triggering the CEL, but emissions will be a tenth of a percent worse ?

MB-CLS500

Hello I have same noise comin from the engine bay I have 07 s550 4matic do you know the part number

S_G7

The part number is in post #4 and #11.

Jason B

Does this also happen on 2010+ at idle.

Weems

I have a 2009 Mercedes-Benz S550 4matic and have the same problem. A slight tapping coming from engine compartment when idling. It is intermittent and speeds up and slows down. What is the best recourse?

njsdavis

I read a thread on this couple years ago when I first joined this site and bought my 2008 s550 4matic. It was pretty much, to put it into my dummy, non mechanic terms, some cord or wire/tube holding wires that ran through there. It vibrates because of its placement and not necessarily the vehicle malfunctioning itself. I think that individual said he went in and wrapped it with some type of heat resistant padding/insulation just to quiet the noise a bit but it is almost impossible to stop the vibrations.


If I have time I will search for that thread, I am working 3rd shift now so I have more time to read, but I sleep all day so that transforms to no time work on my car during the daylight hours until the weekend. And its football season so we know how that goes!! Good Luck

Weems

If you replace the purge valve on a W221 with a newer one for a W222, will it be quiet and the computer not give an error code?

Jason B

I had my purge vale replaced under warranty. Ticking sound still there, but not as bad.

Weems

Was the replacement for a W221 or W222? Because the newer ones for the W222s are suppose to be silent, if put on the W221s

Jason B

Wait, are you saying the purge value from a W222 will fit a w221?

amriyaz

1. Fuel evaporation system, Purge Control Valve (PCV) solenoid is located in the front of the engine (driver side) and looks like this with "MOT" written on it
2. Remove the electrical connector from the top and clean it with electrical part cleaner spray from CRC
3. The input and output tube removes easily by gently twisting. There is a special clamp on one tube that can be taken out with pliers
4. The PCV device is hosted on a rubber mount that comes off easily. Also check if the rubber mount is too loose/worn out can further contribute to the ticking sound
5. Pressure clean both input and output holes with Mass Air Flow (MAF) cleaner and further clean it with a cotton tipped q-tip to remove any residue/buildup
6. If necessary replace the PCV with BWD - Vapor Canister Purge Solenoid Line: BWD Part # CP582 available at Autozone or O'Reiley for $89.99. The O'Reilly URL for the PCV is: http://www.oreillyauto.com/site/c/de...2211&ppt=C0018
7. Following this procedure can substantially cut down on tapping/ticking sound at idle in Mercedes E and S class between 2007 and 2009.

Jason B

Nice. The 2010-2013 also makes this noise, and dealer says that's normal.

bigkev21

Mine sounds like coke bottles rattling, like the ring toss game. It sounds like it's coming from the center directly behind the dash, under the Command. It gets louder when the wind is blowing hard outside. May be the same thing?

ItalianJoe1

Purge valves operate by pulsing voltage, so the tapping is normal operation, but you shouldn't be able to clearly hear it in the car. If they don't want to replace the valve, the only thing I could suggest is trying to short it out with high voltage until it breaks, then take it in to get a new one. Not the most ethical way but it will get it replaced.

If you could insulate it and reduce the noise heard/felt that would be better, as any good working purge valve does make SOME noise. On an S class you shouldn't be able to hear it though, with as well insulated as the car is.