W221/W216 ABC Pressures

[pillow]

Hi all,

I am trying to figure out why my rear struts are making a sort of squelching noise when driving over bumps/rough surfaces.

I have replaced both struts with refurbished ones and the noise is persisting. It is very audible from the top of the struts (inside the car) but next to impossible to hear from outside (windows down).

At first I thought the bushing at the top of the strut was knackered but this is clearly not the case. My second thought is that the hydraulic line into the strut (which is near the top) could be linked and perhaps the pressure and flow of hydraulic fluid in the rear is insufficient for some reason?

Does anyone know what the normal range of pressures in each corner should be?

The pump is at a steady 180-190 bar whilst driving and idling. The front left and right sensor are generally at 70-85 bar, and the rear left and right sensors read about 65-75 bar. The rear left (where the noise is predominantly coming from) had dropped as low as 52 bar on my drive home. When idling all pressures are generally stable at around 85 bar front, and 75 bar rear. The car does not sag or dip or show any issues with the suspension other than this noise.

Does anyone either have a suggestion to what the cause of my squelching struts may be, or know what the nominal pressure should be in each corner?

Thanks all

 

[Aleksejs]

First what is color of liquid if its red its should be changed to new one with green color.
Also regarding thr low pressure check intake valve its fitted between oil tank and pump. Very often this valve are make problems due to dirty oil.

 

[alabbasi]

I was just working on this yesterday with my S55 (W220) and it turned out to be the little ball joint looking thing where the ABC shock bolts onto on on the lower control arm that was making the noise. I filled the boot with silicone spray which made the noise go away (just yesterday) while I order a replacement.

Prices for lower control arms are everywhere. From $90 for a brand I never heard of to $400 for genuine. I don't see any TRW, Lemforder or Febi available which is a bit concerning. If it turns out to the same problem, you're welcome I'm been fracking with this for about 6 months trying to figure out where the noise is coming from. I replaced the bushings on this control arm but that ball joint is pressed in.

 

[pillow]

Green CHF11s fluid. The pump pressure is fine at about 190 bar. It is only occasionally I notice the pressure on the rear left strut being below the other rear strut. The front struts are usually about the same pressure.

Unfortunately I think that control arm is for the front. I don't think there are any ball joint control arms in the rear.