fosmith

I have a 2001 e430 with 116,000 miles. For the past month, my car has been making a low resonating HMMMMMMMM sound while cruising under light load at highway speeds of 40mph and above. It is most pronounced at about 1400 rpm and again at 2100 rpm when applying just a little throttle. An increase in throttle boosts the rpm and the sound goes away. Foot off the gas makes the sound go away too. Sometimes the sound will rise by almost an octave and go back down. Sounds almost like those sonar recordings of whales talking to each other. Otherwise it runs fine and feels smooth.

Anybody have an idea what this might be? Could it be the infamous harmonic balancer problem? I'm going to take the car in to the dealer for an "A" service soon and will ask them to look at this but I wanted to be armed with this groups wisdom before I go in. Any help will be appreciated.

thanks in advance,
Fred

martz

whew...could be rear diff . does the humm originate from the rear?
Possibility also of just a bad wheel bearing.....

ohlord

shifter bushings.
Do not take it to the dealer for an A service.You can easily perform that yourself and clear the fss light.
Or at least if you don't do your own maint. interval work,like simple oil changes,go to a place like the http://www.theworkshopmb.com/
in the bay area or have them come to you with the mobile service.
They charge less than the dealer and are more through and real.


or have them locate the sound and fix it,and then you do the A service.
Plugs been done?
Trans fluid changed yet?
If at 116k miles you are way past due.
MB spec fluid only.

fosmith

It doesn't seem to come from the rear but noises can be tricky to locate. Wouldn't diff be more of a whine, though? And, I wouldn't think wheel bearing noise would vary with throttle inputs.

Guess I'm just going to have to take it to the dealer and trust that they won't rip me off...

Fred

fosmith

But do they serve Starbucks coffee like the dealer does?
Plugs were done at 96K
Trans oil drain and filter done 86K and 96K miles. All done at dealer by PO.

Fred

rhettnash

My 2000 e 430 is doing the EXACT same thing. At 42-48 mph it starts, no vibration, cannot locate orig. but sounds more like coming from rear - just sounds like when your tires hit those rippled out of lane indicators on the highway (just the sound) and hums - changes octives as mentioned. Started two weeks ago, but now getting worse and doing it 70-80 mph. Once you let off the accelerator or press more sound goes away. Took it to the local only MB indy shop and the owner rode with me and could not figure it out. He drove the car with me for 20 + min trying to locate sound. He checked the car over and looked for any lose body molds, and to see if anything could be vibrating - though he agreed with me if that was the case, it would only get louder when I accelerate. I am to go back next week as he researches the possibilities.
He mentioned it was not the bearings, as I asked that too, cause the sound would be constant and not dependant on accelerator pedal.
Please keep us updated, as I will too, on what is your vehicles condition. In my case, I work out of my car marketing, so I do not want to take a chance and something major happen. Thanks

fosmith

I took the car to the dealer this morning for an oil change ($89.95 instead of $275 for "A" service) and had them look into the humming noise. I just got a call from the service rep saying that the differential bearings are starting to go and that the repair is to replace the diff assembly. Parts, $2400, labor $1000. His recommendation was to keep driving the car until it gets much worse. He said it could fail and strand me but that was unlikely. More likely, he said, was that it goes another 50,000 miles before it really needs to be fixed. Does this sound reasonable?

Fred

martz

when was the last time the diff fluid was replaced? ??? If unknown,
I would replaced the gear oil and probably consider a thicker viscosity....

fosmith

Never, I think.
That's my next move...
Fred

rhettnash

I had mentioned the fluid dif. fluid replacement to my mechanic. My wife's AWD honda element (please don't ask!!!!) was making a some what similiar noise, but only when turning, almost grounding sound though. The dealer informed me that they could replace the diff. fluid for 90$ and it would stop it. I didn't believe them since it only had 38,000 miles (warranty still in effect on powertrain) on it. Got another opinion at an Indie Honda shop by my house, he called another dealership because he thought it was BS too, and they suggested the same. Oil change and diff fluid changed out - 40$ total at his shop and the sound went away. The mechanic said the diff. fluid appeared to be transmission fluid if not something similiar!!!
I will see Monday on the MB - Good luck

ohlord

mobil diff fluid,diy on benzworld.org,with added suggesting on the little boat pump to fill it easily after drained.
Rare to have a bearing failure and you are due for the fluid change.
http://www.mobiloil.com/USA-English/..._75W-90LS.aspx
is plenty thick enough and will quiet down the problem,if it is even a problem.Which if it came out of the mouth of a service rep,I doubt

"GOT CODES?"

Brau0318

I hate to bring back an old thread but better then starting a new. I'm having this same problem! Although it does get worse as I increase my speed, it still hhmmm's when I take my foot off. The transmission is shifting fine and other then the slack "clunk" at 30mph everything seems fine. It's quite anoyying, I just got back from a road trip and it was just oscillating in my head like a bass note.

fosmith

The humming noise went away after my right rear cat started rattling and I replaced the cat. I'm thinking that it was the matrix in the cat coming loose and vibrating against the housing at certain engine speeds. Once the matrix broke loose, the vibration noise went away. I'm now at 148K miles and I'm starting to hear it again so I'm waiting to see if the left rear cat starts rattling soon. We'll see...

Fred

Brau0318

I did not expect the op to respond on such an old thread. Thank you though!! I will check mine out. I just got stuck in a snow bank and had to dig myself out. I was thrashing at the exhaust in the cross fire of hacking at the ice an snow so maybe it had something to do with it. I dont know, but thank you for responding

tblasko

Just want to say I'm having the EXACT same problem. I am going to see about solving it as I'm not sure what's causing my problem, yet, and then come back and post another reply. Wish me luck!

ohlord

have a 1995 E320 you won't have the same problem,it is a different model entirely. You have the M104 engine,different exhaust,different transmission,different injection,,,
So are you in the correct forum?
Or do you own a w210 and not list it in your profile?

JohnE320

Good to know. My '02 makes a consistent noise coming from the rear end. I think it's the bearings. I may jack it up and take a look at the rear diff. No change in the noise when I increase or decrease the gas. Worth a look though.

r0gue

I'm running into this now. I was feeling it might be behind the transmission itself, but I thought perhaps that was just wishful thinking.
Any further updates from your findings? I did have the rear diff fluid changed preventative back in 2018 when I bought the car. Though I imagine they didn't use a heavy diff grease but rather than trans fluid as someone mentioned. I hope it IS the exhaust and not the driveline or God forbid, the transmission.

Thanks all!

Plutoe

I think the only way you will be able to correctly locate the noise area is to put the car on a lift and do some low speed tests

r0gue

Can they run the car in gear while on a lift? I guess they could if someone is willing to take the ride up with it.