Degrading Ride

[Ken Griffith]

I have an S500 that I have owned for about 6 months. Like every new car owner, I loved the ride. The problem now is I think it's ride is degrading.

I have replaced the shocks with new factory shocks. It just doesn't seem to absorb the bumps on the road very well. When I hit a change in the road conditions it jolts the car severly(the ride is very smooth on a good road). It's like it doesnt have shocks at all. Seems particulary bad on the right rear.

Any ideas of where to look?

I am a new mercedes owner, so a question? Does my 96 S500 have any special suspension systems that might have gone bad(i.e. automatic load leveling, etc)

KG

[sixto]

On an MB with self leveling suspension such as a 96 S500, a stiff ride generally indicates failing or failed accumulators. On older models it's a relatively cheap and easy fix. With a W140, who knows?

Sixto
91 300SE
81 300SD

[Ken Griffith]

What are accumulators? Any checks I can do to see if they are failing?

By the way, how does it self level?

Signed
Ignorant
KG

[ymsin]

Funny how I felt the same with the 126 aftter having replaced all the front end bushes. I was told that this is relatively normal. And when I said that it was much smoother before, I was told (with much ease) that the suspension was too soft then ...

For now, I just take it easy at road bumps.

[sixto]

Ken,

I don't know about the W140 specifically, but the system on older models consists of a hyraulic pump, a leveling valve, struts and accumulators. The pump provides pressurized fluid which is directed by the leveling valve to the struts. The leveling valve differentiates between components in the rear suspension to determine if the rear is sitting high or low. It adjusts pressure to the struts until the rear is sitting at the 'right' height. The accumulators are spheres with a diaphragm separating fluid from nitrogen. When the struts take a momentary compressive load such as going over a bump, the fluid compressed out of the struts goes into the accumulators. The nitrogen makes it progressively more difficult to accept more fluid in the accumulators so the car doesn't bottom out completely. The accumlators are the hydraulic equivalent of springs. There are coil springs on the rear suspension as well, but they won't support the car without the accumulators.

Older systems don't have the sophistication to level the car left to right. You never know with a W140. Older leveling systems have no reference to gravity so they won't try to level the car on a sloped driveway. Again, the W140 is not just any car.

When the suspension gets stiff, it's typically the accumulators that are failing or have failed. In most cases, the nitrogen leaks out leaving the accumulator full of fluid and unable to absorb the compression of the strut.

I don't know of any practical in-situ test of the accumulators other than a stiff ride. Any MB tech should recognize the symptoms immediately. MB recommends replacing the hydraulic system fluid periodically.

Sixto
91 300SE
81 300SD