W124 Estate Self Levelling Suspension

[davecrane]

Hi, need some education - think the self levelling suspension is leaking, the reservoir is down to about 1/2 inch fluid. Can I replenish with normal brake fluid? I think it may be the offside shocker that's leaking (not positive due to wet weather) is it going to be expensive? Also where does the pressure come from - does it use the power steering pump? And is it a flowing system (I assume the fluid returns back to the tank via the filter at the top?) Thanks

 

[television]

Hi Dave and welcome Yes it uses the power steering pump,, some others that know the system well will give you better advice than me.

In the link below,,it all opens after BM and you have all of the working parts there,, often leaks are a rusted oil line


http://www.detali.ru/cat/oem_mb1.as...&GA=722.320358&GM=717.430&CT=F&Cat=506&SID=32

 

[Bolide]

Hi, need some education - think the self levelling suspension is leaking, the reservoir is down to about 1/2 inch fluid. Can I replenish with normal brake fluid?

Use the correct MB fluid only

I think it may be the offside shocker that's leaking (not positive due to wet weather) is it going to be expensive? Also where does the pressure come from - does it use the power steering pump? And is it a flowing system (I assume the fluid returns back to the tank via the filter at the top?) Thanks

Suspension legs are expensive new and cheap second-hand. I'd replace the top mount rubber bushes both sides while you're doing it

The pressure is provided by a pump either driven off the nose of the cam or in the same housing as the power steering pump

It's possible there is no leak but a sphere has failed and filled up with hydraulic fluid

Nick Froome
www.w124.co.uk

 

[Jay Gee]

Try here also-I believe that this system has certain similarities with the Merc.one. Please take this in the spirit it was intended,i.e. as an avenue to explore http://www.actwin.com/toaph/citroen/work/work.html

 

[davecrane]

Thanks to all who have replied so far - any recommendations for an independent Merc garage in the Derby area?

 

[Number_Cruncher]

Sorry - long post alert!!

One way to view the self levelling system is that it consists of two parts, a fast response part, the struts and the spheres, and a slow response part, the valve and the pump.

-------- The fast, or dynamic part of the system ------------

The devices which look like shock absorbers or dampers *aren't*. They are simply hydraulic rams or pistons. Whenever the suspension moves towards bump, fluid is displaced from the rams back up the large bore piping to the spheres which are mounted inboard.

The spheres contain a diaphragm and a damping valve. The damping valve is fitted on the fluid side of the sphere, and any fluid entering or leaving the sphere must pass through this restrictive valve.

The dry side of the sphere contains pressurised Nitrogen, contained by the diaphragm. Fluid entering the sphere, having passed the bump orifices of the damping valve then displaces the diaphragm, reducing the volume available for the Nitrogen, and increasing its pressure.

The coil spring supports the unladen weight of the car, and any extra force to support extra weight comes from the fluid pressure in the hydraulic rams. All of the damping is provided by the damping valves in the spheres.

-------- The slow, or quasi-static part of the system ------------

The levelling valve mounted between the anti-roll bar and the vehicle body has 3 operating positions, raise, lower, and hold.

While the suspension is low, the valve is in the raise position, and fluid is admitted from the high pressure pump to the sphere / ram part of the circuit.

While the suspension is high, the valve is in the lower position, and fluid is returned from the sphere / ram system to the reservoir.

When the suspension is just right, the sphere / ram part of the circuit is isolated from the pump and reservoir. The fluid flows from the pump to the valve, and returns to the reservoir.

The pump has a low displacement, and the pipework to the levelling valve, the valve itself and the pipework (with inbuilt restrictors) between the valve and the spheres which all mean that the pump cannot react quickly to dynamic changes like bumps, but can respond to longer term changes like responding to a change in vehicle loading.

So although the suspension remains at a fairly constant mean height, and so the mean load on the spring is also constant, the amount of load borne by the mean hydraulic pressure in the sphere / ram system does vary and it depends on the imposed loading.

------------- Practical points -----------------

It's quite common for the pipework to corrode, especially just ahead of the rear axle. If these pipes have failed, it's probably worth only mending the rusty section, and making some pipework joints with something like a Swagelock fitting.

As the hydraulic rams are just rams, there's no real reason to replace them in pairs - as long as you are replacing like with like. There are different rams fitted to vehicle with sports suspension.

Leaking, or seizure are just about the only ways that the hydraulic rams can fail.

Problems with hard, bumpy, high, and bouncy suspension are usually caused by failure of the spheres. Many garages don't understand the system, and when the back end of the car bounces, they replace the struts, because they look like dampers!, and only after they realise they haven't fixed the fault do they transfer their attention to the spheres, and of course, the poor customer pays for their tuition!

Failure of the spheres is probably the single most common fault with the system.

It's worth using the correct MB oil to ensure compatibility with the seals in the system.

As I do all the work on our E300D, I can't recommend a garage in Derby, but, it might be worth talking with German Automotive on Ascot Drive.

 

[television]

I will ask Anyweb to make this excellent write up a sticky

 

[Taps]

Hi, new to here

I have just picked up a 200TE today, drove it home and seems I have a problem with my Load Leveling, it looks like and feels like its pumped its self up to full height and stopped there

Was fine when I picked it up, it has been stood a year, the further I got towards home the ride became shall we say not as I would expect from a Mercedes :grin:

Any ideas where to start looking for the problem would be helpful

Taps

 

[television]

Hello and welcome,, do check the height valve on the rear axle 59 in the link the rod 41 controls the height


http://www.detali.ru/cat/oem_mb2.as...GM=717.433&CT=F&cat=15U&SID=32&SGR=195&SGN=04

 

[Taps]

Hello and welcome,, do check the height valve on the rear axle 59 in the link the rod 41 controls the height


http://www.detali.ru/cat/oem_mb2.as...GM=717.433&CT=F&cat=15U&SID=32&SGR=195&SGN=04

That's brill, thanks for that, could all have seized up where its been standing for so long perhaps will let you know the outcome.

 

[Bolide]

If it's super-hard and high replace the spheres. If it's totally undamped replace the spheres

But check for fluid leaks & broken height corrector / linkage first

Nick Froome
www.w124.co.uk

 

[Taps]

If it's super-hard and high replace the spheres. If it's totally undamped replace the spheres

But check for fluid leaks & broken height corrector / linkage first

Nick Froome
www.w124.co.uk

Well its not rock hard, I can still make the back bounce a bit, ride wise the back end feels like its hopping at every bump, was a very strange ride home

 

[davecrane]

Number Cruncher, excellent description of the system, thank you for the education!

 

[Number_Cruncher]

Thanks Dave

As questions about this system are so common, I wanted to jot down the operation of the parts of the system that I have some sort of grasp of. I'm sure that people like Nick (Bolide) would have far more detail to add.

One point of note is that the large bore metal pipes between the rams and the spheres are about £70 each, so, go steady with them!

 

[Taps]

Hello and welcome,, do check the height valve on the rear axle 59 in the link the rod 41 controls the height

You was spot on with checking the link rod m8

Have temp fixed it until I can get a new rod , ride height has come back down.

Tried it up the road and all back to how it should be.

Thanks very much for the advice

 

[dojan]

Hello, also new here
I am about to change the spheres on my E 250 D estate 95. I intend to keep the car forever, so can anybody give me details how to do the job properly

Andrej

 

[stumpy]

If the height control arm is u/s does the height control valve default to neutral thus meaning that the rams don't level the suspension?

 

[turnipsock]

I thought the suspension had its own pump.

Do you know where the leak is coming from, or did I miss something?

My bet would be some of the pipes which are fairly easy to replace.

 

[television]

I thought the suspension had its own pump.

Do you know where the leak is coming from, or did I miss something?

My bet would be some of the pipes which are fairly easy to replace.

I believe it shares the steering pump but has its own tank

 

[The Crooner]

Mine's right at the front of the camshaft - 1992 230TE

Tony