2009 s600 engine sound louder after 25 minutes driving
Thread Starter
Junior Member
Joined: Aug 2024
Posts: 21
Likes: 7
w221 s600
2009 s600 engine sound louder after 25 minutes driving
Hi folks this could potentially be a very stupid question, but I got this interesting symptom that I'm not sure if it's a cause for concern or not. After around 25 minutes of city driving, pretty reliably, the engine bay suddenly sounds louder. When engine RPM goes up you can hear very obviously a whining sound goes louder. It was not like this in the first 25 minutes during which all sounds are pretty well insulated.
I'm guessing at around 20-25 minutes mark some additional pump starts to run (whose speed is proportional to engine RPM) or turbos behavior changed, and that sound is not well insulated? I don't notice any other difference other than the sound. What could it be? Thanks!!
I'm guessing at around 20-25 minutes mark some additional pump starts to run (whose speed is proportional to engine RPM) or turbos behavior changed, and that sound is not well insulated? I don't notice any other difference other than the sound. What could it be? Thanks!!
MBWorld Fanatic!
Joined: Aug 2014
Posts: 5,315
Likes: 1,672
S500
the only thing I can think of is the cooling fan - on full chat that can make lots of noise
have you checked the level of the charge cooler.... that likes to loose coolant
have you checked the level of the charge cooler.... that likes to loose coolant
Last edited by BOTUS; May 27, 2025 at 02:09 PM.
MBWorld Fanatic!
Joined: Feb 2012
Posts: 2,607
Likes: 1,208
From: Phoenix
222 S-65
OP it will be equipped with ABC. The nitrogen bomb (pressure dampener) that threads into the duo-pump may be losing its nitrogen and making for noise. Ten minute repair.
At idle as it makes the noise.... long screwdriver applied to A/C compressor, Duo pump, alternator, behind each of the bearings in accessory drive...
Find it.
At idle as it makes the noise.... long screwdriver applied to A/C compressor, Duo pump, alternator, behind each of the bearings in accessory drive...
Find it.
