Suspension query on w116 280SE

[NGK]

Hi all,
I am a bit confused by the self-levelling and hydropneumatic terms.
Is my vehicle's suspension affected by oil and air pressure or just oil, as I know and can see this oil supply tank and pump?
I am told that the rear spheres will probably need replacing, as the ride is noticeably rocky and firm, but is there a way to test them or check to see if they are really stuffed?
Also, I haven't yet noticed them, but would I presume that I have a set of spheres on the front as well, serviced from the same supply tank?
Any advice or suggestions would be greatly appreciated.

cheers,
ngk

[TJ 450]

To check the spheres at home, you need to remove the hydraulic pressure line to the strut and poke a rod through the orifice. It shouldn't go in far, otherwise the sphere is dead and full of fluid.

You will lose fluid and as you're probably aware, ATF isn't suitable as it holds air and the car will sag/wallow as a result.

Tim

[NGK]

Thanks Tim. As a matter of interest, what happens when you remove the pressure line, does fluid go all over the place?

cheers,
ngk

[TJ 450]

Yes it does. The car should also be supported with the wheels off the ground, otherwise the suspension will drop right down crushing anything beneath the car. The springs will compress under the weight of the car despite their appearance. Personally I don't think it's worth doing that test as the ride characteristics will tell you that the spheres are not functioning. The spheres on my SLS 450 are due for replacement and it has suboptimal damping characteristics and wallows after a few hours of sustained cruising (110km/h +).

On the "SLS" system there is a reservoir and pump up front, then a leveling valve, two spheres and two struts at the rear. There is a filter integral to the reservoir cap on the return line. This is the same as the filter for the 6.9 and is inexpensive. These are all the components of the SLS system. IMHO it is quite basic and parts are relatively inexpensive and easy to obtain, nothing to worry about.

The actual "Hydropneumatic" system is only on the 6.9 and W126 500/560SEL and that is far more complex with three spheres up front and a myriad of other components that you needn't worry about.

Tim

[NGK]

Thanks Tim, a very comprehensive and informative explanation. Might leave it to more capable hands.

ngk