High Pitched Engine Noise -- HELP!!!
Anyway -- on to the question. I picked up a 2007 S550 with a sport package with 55K miles. The car is very clean and everything looks good.
Drives great as well -- except that I noticed a very high pitched engine noise (sounds like its coming from the front left side). You can hear it at low speeds around 2500 RPM. I get the noise accelerating and decelerating.
Planning on taking it to the dealer next week -- but wanted to see if anyone else has experienced anything like this.
Thanks.
S-B-13.22/01d JUL08 Up to engine #272xxx 30 476520 RPM dependant grinding, howling, whining or high pitch whistle noise coming from the front section of engine, the upper idler pulley will be replaced.
Service Campaign 2008070002 AUG08 – 164, 164.8, 171, 203, 209, 211, 216, 219, 221, 230, and 251 Dealer will replace the existing V-belt upper guide pulley with one that is optimized for noise reduction (guide pulley – part #A272202101905). Approximately 192,941 vehicles affected.
See https://mbworld.org/forums/new-s-cla...ns-date-3.html




From the description you gave us it is a pulley.
I also remember almost the same thing on my RIP S430.
Easy (dealer) fix.
Anyway, let us know what it was.
Has it been this way from day one???
From the sound it makes -- I would not be surprised if it were the belt/pulley issue.
Thanks.
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The Hydraulic Accumulator/Shock Absorbing Unit mounted on top of the Active Body Control Unit went bad. Cost to replace -- $1,100. I guess it could have been worse. Good news was that otherwise -- they said the car was is good condition.
I was hoping it was the pulley/belt issue -- but no luck.
Anyway -- thanks to everyone for the helpful input.



