W215 pulsation damper noise

[Frank86]

Hopefully someone hear can help, car is a 2003 cl600, I have the whirring sound that goes with engine revs, I did a lot of searching online and forums etc. nearly every thing I came across had the same conclusion so I changed the pulsation damper/accumulator behind the drivers side wheel for the ABC suspension.
Noise is still there, I have seen there is another pulsation damper attached to the ABC pump itself, could this be causing the noise?
There is an ABC pipe just behind the rad down low on the bottom panel that is blocked at the end which I’ve come to learn is an expansion pipe and there seems to be a vibration/humming coming from that pipe.
Does anyone know if this pipe is connected to the pulsation damper on the pump and the whirring sound is travelling through this expansion pipe?

 

[Uky]

Having owned a CL500 W215, I can only speak out of own experience and from the document I got from a friend at the local Mercedes service center.

I had a problem with the pulsation damper in my car. It wears out after some 100.000 km.

In the W215 with a worn-out pulsation damper, the humming noise (with an M113 V8) should stop/cease at revs above 1800 RPM's when the car is in neutral and you press the gas pedal.
I think that a similar RPM is valid also for the V12 engine.

Mercedes does not specify a service interval for the hydraulic flud but it must (!) be changed regularly as it looses its
properties. If the oil in the container is grayish and smelly you should have it changed. Fresh oil is clear and green.
A failed coaxial pump will cause metal debris to spread in the hydraulic system. This will be very expenceive to fix.

Also the filter attached to the lid should be replaced.

 

[Swotty]

Probably way off beam as I've not heard this, having had to change the ABC/steering pump and the 2 front struts , but I did have a kind of noise/perhaps humming when I first got the car. Turned out to be the plastic tube right at the front of the engine just forward of the plastic cover and which I believe is the secondary air pump for the engine? Pushed it back on and no problem since.

Does it sound possible it's just an engine noise, rather than the ABC?

 

[Frank86]

Probably way off beam as I've not heard this, having had to change the ABC/steering pump and the 2 front struts , but I did have a kind of noise/perhaps humming when I first got the car. Turned out to be the plastic tube right at the front of the engine just forward of the plastic cover and which I believe is the secondary air pump for the engine? Pushed it back on and no problem since.

Does it sound possible it's just an engine noise, rather than the ABC?

I would be fairly certain that it’s ABC related. There’s 86k miles on the car and as far as I can see it’s the original pump.
Does the pump start to make noise if they are wearing out?
This whirring sound is definitely going with engine revs and more noticeable inside the cabin

 

[Swotty]

I would be fairly certain that it’s ABC related. There’s 86k miles on the car and as far as I can see it’s the original pump.
Does the pump start to make noise if they are wearing out?
This whirring sound is definitely going with engine revs and more noticeable inside the cabin

Difficult to recall exactly but believe it was a mechanical whirring noise which increased with engine speed and iirc, when the bonnet was opened you could trace it to the front-ish of the engine.

Sorry, 'twas when I first got the car 9 years ago! Hope it is indeed something as simple and inexpensive for you.