W124 Estate -can I drive with self levelling down?

John Turner

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S124 250TD (1989), S124 E300TD (1995), S211 E320 cdi Sport (2007)
My W124 estate has corroded rear suspension pipes (from spheres to struts) and a broken valve control rod on the self levelling suspension. Took to garage to have work assessed and parts ordered. On way back from garage, offside pipe leaked hydraulic fluid. The car soon dropped onto its springs (level on both sides). Wheels still have clearance in body work, but car has little shock absorbance. I managed to limp it home (a mile or so) before 3/4 of the fluid had gone. I now need to get it to the garage (a distance of 20 miles of dual carriageway). If I understand the system correctly, the car is now resting only on its springs but has no 'slow' self levelling system in operation. It cannot drop lower unless the springs break, and cannot rise without fluid (and a broken valve control rod).
Two questions:
Is it safe to drive that distance? (I suspect not - even unloaded).
Can I do harm to the springs or struts if I drive it slowly in this state? (I suspect so)
I do not want to take any risks to anyone else, me or the car!
Thanks for your advice.
 

Richard Moakes

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1991 R129.066 M119.960; 2005 W164.175 M113
Your problem is running the pump dry.

If you move the sls valve control rod so that the fluid is simply returned to the reservoir then you will avoid that.

As for driving with the suspension lowered, then I suspect you will be fine if you drive slow and avoid any speed bumps.

Good Luck
 

Myros

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take acouple of litres of SLS fluid with you

and top up on the drive. expensive and oily, but at least you will get there with the pump intact.
Any good commercial hydraulics factors might be able to help you with pipes and the like and save you the long trip.
MBs pipes are about £75 or more.
 
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John Turner

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Thanks Richard and Myros.
From what Richard says, I am assuming that if I can get the snapped control rod to the middle (level) position, then the fluid will just circulate from reservoir to valve, and therefore I will not lose anymore. My concern is that the rod has snapped, and so I do not know whether I can position it level. The car is now too low to get under.
I note from Number Crunchers response to the sticky post on W124 self levelling suspension that '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.' I assume from this that I can drive the car slowly if I avoid bumps, but that I am going to be feeling seasick due to the lack of damping!
My route is smooth tramac with no speed bumps, but I am very concerned about additional damage to the pump or springs (or possibly the rubber mounts above the struts (?) ). I imagine that it must be possible to disconnect the pump? Would this be a sensible thing to do? I have collected some of the leaked hydraulic fluid but it does not look that clean, and so I am reluctant to put it back in. I do not want to buy new, and watch it get pumped out again!
Thanks
John
 

Richard Moakes

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1991 R129.066 M119.960; 2005 W164.175 M113
Your assumption is correct, you need to ensure the arm on the valve is in the level position. I suspect the rod from the arm to the antiroll bar has snapped, so you ought to be ok.

The coil springs are the last resort, they will barely support the unladen weight but the rear of the car will be very low, and you will have no damping, so maybe you will need those seasick pills!

Don't put old fluid back in, if you have a GSF near you, then you should be able to pick up some ZH-M fluid from them at a reasonable price.

Don't know if you can disconnect the pump, on my engine it's driven from the main drivebelt, and on some engines it is driven from the camshaft, not sure which it is on your car.

Good Luck.
 

Myros

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I think it's a tandem pump

and does the power steering as well ( discreet reservoirs of fluid) If you disconnect, you'll lose your ps.
I drove 20 miles like this to my garage ( level sensing link not broken) with a leaky pipe and lost 3/4 litre of fluid in about 30 mins. i stopped half-way and refilled the reservoir.
The last time I bought a litre, 3 years ago, it was about £10. Must be more by now.
 

Number_Cruncher

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>>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.'

I was over-simplifying slightly. The difference is quite academic though.

The springs *almost* support the weight of the car. To level the car up, and provide the last little bit of lift, there is a small minimum pressure which keeps the rubber diaphragm in the sphere just off its stop. Without this so-called basic pressure, the spheres wouldn't work properly with an unladen car.

It won't make a huge amount of difference where you set the control lever, and for a few miles, you'll not do any damage to your pump if you run out of fluid.
 
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John Turner

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OK, I have jacked the car up, inserted axle stands, and got under to put the control lever into the middle (level) position. However, after dropping it down again, and starting the car, I am noticing hydraulic fluid dribbling out once more. Should this happen, or do I need to let it run for longer? I only have about 25% of the reservoir full, and no easy source of more ZH-M fluid. I can see no way to disconnect the pump and probably have the same arrangement as Richard and Myros explained. The springs look good, but I do not want to damage the pump. Looks as though I am down to risking a 20 mile drive or arranging for collection.
 

Number_Cruncher

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Disconnect both supply and return pipes off the level control valve, plugging the open ports to prevent contamination, and, using some flexible pipe and jubilee clips, loop them together. Without the level control valve in the circuit, the pump will develop (virtually!) no pressure, and fluid will just be circulating slowly in the loop.

Sorry to say that these large bore pipes between the spheres and the hydraulic rams aren't cheap.
 

Richard Moakes

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Disconnect both supply and return pipes off the level control valve, plugging the open ports to prevent contamination, and, using some flexible pipe and jubilee clips, loop them together. Without the level control valve in the circuit, the pump will develop (virtually!) no pressure, and fluid will just be circulating slowly in the loop.

Sorry to say that these large bore pipes between the spheres and the hydraulic rams aren't cheap.

A very simple and effective answer from number cruncher, I wish I had thought of that :Oops:
 
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John Turner

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Thanks Number Cruncher - sounds an excellent solution and well worth a try.
Regards
John
 
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John Turner

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I thought that this was a high pressure system, but I take it, you are saying that the pressure will be low without the level being sensed. My concern was that a jubillee clipped join might not hold against the pressure, but I am willing to have a go.

Regards
John
 

Richard Moakes

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It's a high pressure, low flow rate system.

The return line back to the reservoir will not present a restriction, so the pressure developed against the rubber hose and jubilee clips will be low.
 

Number_Cruncher

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It's a high pressure, low flow rate system.

The return line back to the reservoir will not present a restriction, so the pressure developed against the rubber hose and jubilee clips will be low.


Quite so. A tap only sprays when you hold your finger over the end!


Taking the valve out of the system makes it a low pressure, and ever so slightly higher flow rate system.
 
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