2001 NA-V12 S600 with strange noise
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Newbie
Joined: Aug 2011
Posts: 12
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2001 S600
2001 NA-V12 S600 with strange noise
There is a strange resonant hum coming from the front of my car that is driving me insane. This happened quite rapidly, one day nothing next day hum and it has been getting louder since. It appears to get louder the hotter the engine is but that could just be my imagination. It does not appear to affect the power, however my normally gloriously quiet cabin is filled with a hum that makes me want to rip my ears off. At first I thought it might be a pulley bearing so as a preventative measure I replaced the serpentine belt and had the mechanic check the pulleys, no joy, they turned freely. The noise changes pitch and volume with RPMs and is most resonant in the cab from 1400-2200 RPMs but seems to go away after 2200ish but since you have to be going 80MPH....At those RPMS the roar of the engine is likely just masking the sound anyway. The fact this happens with the vehicle in park seems to exclude the possibility of transmission or a wheel bearing...Any suggestions would be most welcome and if you say its the engine don't expect a reply because I will be looking for a building to jump from. 
JK
JK
Super Member
Joined: Feb 2007
Posts: 809
Likes: 74
From: Dallas, TX
2008 E63 wagon (1 of 62)
There is a pressure reservoir in the ABC system under the car, near the passenger side lower control arm. The belly pans will have to come off to get a good look at it, but once you see it, it looks like a big black ball (about 4-5" in diameter) attached to a small valve body with a pressure sensor hooked to it. The inside of the that reservoir has failed causing the issue. When you replace it or have it replaced, I would also suggest doing a flush of the ABC system with a new filter to finish it off.
At idle, you probably wont be able to hear the noise you are talking about, but it is most noticeable from about 1200 to 2000 rpm or close to that like you describe.
At idle, you probably wont be able to hear the noise you are talking about, but it is most noticeable from about 1200 to 2000 rpm or close to that like you describe.
Thread Starter
Newbie
Joined: Aug 2011
Posts: 12
Likes: 1
2001 S600
Thank you for the reply, sounds a LOT better than a cam bearing...but just barely...I performed a search for abc pressure reservoir and did not come up with anything is there another name for it? Part number would be ideal.
Why do I think this is very expensive to repair?
Why do I think this is very expensive to repair?
Senior Member
Joined: Mar 2011
Posts: 277
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From: Nebraska
2005 CLK500 cab, 2004 S600 designo mocha
I have heard using a short (3'-10') garden hose or such is a great tool for zoning in on which component is making the noise?
How is your power steering reservoir doing on fluid? If you ran it dry, that could be the cause. Open the hood and try to get a better idea from where about the noise is coming from.
How is your power steering reservoir doing on fluid? If you ran it dry, that could be the cause. Open the hood and try to get a better idea from where about the noise is coming from.
