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The problem continues, the car lists to one side, the drivers side is too low.

We thought we'd found the problem, that being two different rear springs, but replacing them both, fitting new suspension pads front and rear hasn't solved the problem.

The car is lower both front and back on one side, all springs are now good, raising the rear corner manually raises the whole side, so we think we have isolated the problem to one rear corner.

What next? The SLS seems to be ok, and the ride is ok as far as I can tell, is it worth replacing the spheres and / or SLS strut? I understood that the spheres are like dampers, the hydraulic struts controlling ride height, but it was unusual for either of these to give ride height issues.

The SLS pipes are all fine, no leaks that can be seen, and the fluid level does not need topping up.

One "cheat" would be to replace the newly replaced 2 tag rear rubber spring cup with a 3 tag one, which I guess would raise that corner, but, I suspect, be a cover up rather than cure.

Any advice would be greatly appreciated as this is starting to become frustrating.

Thanks in advance
 
A completely collapsed sphere (ie the membrane inside the sphere has become permeable so all the gas that pressurises the sphere has gone) will not be pressurising anything so may affect ride height (it is the self-levelling as well as damping). If the sphere has lost pressure once the ZHM is topped up it won't then lose more fluid so hydraulic levels will appear normal.

With functioning spheres ride should be absolutely fluid. Any obvious springiness is sphere related - bounce is a feature. Any history to show when they were last done?

How much ride height difference is there?
 
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There's probably 30 - 40 mm, so quite pronounced

I'd thought the struts adjusted the height but am certainly here to be proven wrong, the history is all in the car so I'm unable to check presently

Thanks Charles
 
http://www.w124performance.com/service/w124CD2/Program/Chassis/32-0501.pdf is an explanation of how the system works, cliff notes version being that the spheres do most of the springing and damping*, the coil springs set the basic ride height and hydraulic pressure in the struts is used to lift the back (gravity lowers it when the SLS valve diverts more oil back to the resevoir allowing pressure to drop).
If/when the nitrogen in spheres escapes the nice supple rising rate 'gas spring' is replaced with incompressible oil hence a hard and bouncy ride. The back won't sink with flat spheres unless the fluid level is properly low or something else is going on, not uncommon for the back to be a bit higher than usual with flat spheres (incompressible oil replacing soft gas spring...). Not 35 - 40mm higher though

What happens if the SLS valve is disconnected and the system pressure 'dumped' by moving the valve to its discharge/emptying position? Obviously the car needs to be on wheels and high enough to avoid risk being squashed. If both sides don't drop then i'd be looking for semi seized suspension linkages or maybe even a bent SLS strut etc

* MB describe the struts as dampers and i'm sure they have valving in them much like 'regular' dampers do however the valving in dampers works by restricting oil flow (converting KE into heat) and if the nitrogen has escaped and the volume it occupied is full of incompressible oil then the system is effectively hydraulically locked i.e. little to no oil flow into and out of the spheres (acting against the nitrogen bladder) so little to no damping...
 
What happens if the SLS valve is disconnected and the system pressure 'dumped' by moving the valve to its discharge/emptying position?

I'd say that was the first question to answer

If you can put the car on a flat surface and do some measurements front & rear with a plumb bob then you may find where the discrepancy is

I have come across bent struts in the past. A good test is to jack the car up & allow the rear wheels to droop, then try raising & lowering the rear wheels in turn with a jack. If they go up or down in jerky steps you may have a bent strut. You may also find a seized bearing at the foot of the strut

However I doubt either thing could prevent the car from sitting down on the rear springs

I'd look for the unexpected: collapsed rear subframe mounts, mismatched rear struts, front end out of whack, etc, etc

Assume everything that's been done to the car before is wrong

Nick Froome
 
Thank you both for your replies

We've already quickly measured suspension mounting positions and looked carefully at the mounting points and couldn't find anything wrong but I guess we are going to have to go back to the beginning and start eliminating, I'm even wondering if one side can be full of water in the boot or something similarly weird

Thanks again
 
Steve

I went through a "similar" scenario with my C55 Wagon. We had the rear subframe off the car and bushes replaced and frame measured, floor pan checked, new springs and pads. In short we did everything humanly possible to find the issue and failed.

Eventually we had the car "jigged" this showed the car was twisted, fractionally so, but twisted it was. Had it pulled out on the jig and problem was resolved.

Speculation was that the car had spun into a kerb on the rear wheel, transferring the shock through the car rear right to front left. Have you checked all the panel gaps for synergy?
 
I went through a "similar" scenario with my C55 Wagon...

Eventually we had the car "jigged" this showed the car was twisted

I think this is a possibility but would think that accident damage would also be visible. The amount of energy you'd have to put into the bodyshell to bend it would be pretty high

I have a parts car that had a side impact hard enough to put a ripple in the transmission tunnel behind the front seats. But the intrusion into the door & sill is 6-8" and the car is very obviously bent

If the car has had an impact sufficient to bend it you'd assume it would be a Cat D and/or have some visible repair marks.

But, of course, assume nothing...

If you drive behind the vehicle on the road, does it drive straight? Have you checked the wheel alignment on a Hunter machine? If it has any real alignment oddities that might point to the car being bent

Nick Froome
 
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Thanks again for the pointers, unless it was repaired to a high standard, it looks unlikely that the car has been bent, the panel gaps are good, there is no sign of welding underneath, in fact, the welding that has just been carried out in the front inner wings is the first the car has had by the looks of things.

I'm not ruling out Bruces suggestion of a kerning that may have knocked out the rear geometry, the mechanic is going to have a closer look tomorrow.

I do wonder if I am over complicating this, the spring pads are available in varying thicknesses, is this for a situation such as this?

Nick, it doesn't drive well, this levelling of the car was the first in a 2 part procedure, the second being to stop it wandering across the road, the mechanic discovered the lower wishbone mounts at the front of the car were loose, and the mountings have worn, so he is going to sort that once (if) the car ever sits level, however, the car doesn't crab or pull noticeably to one side really.

Thanks again for the continued help
 
CCAALLVVIINN said:
Thanks again for the pointers, unless it was repaired to a high standard, it looks unlikely that the car has been bent, the panel gaps are good, there is no sign of welding underneath, in fact, the welding that has just been carried out in the front inner wings is the first the car has had by the looks of things. I'm not ruling out Bruces suggestion of a kerning that may have knocked out the rear geometry, the mechanic is going to have a closer look tomorrow. I do wonder if I am over complicating this, the spring pads are available in varying thicknesses, is this for a situation such as this? Nick, it doesn't drive well, this levelling of the car was the first in a 2 part procedure, the second being to stop it wandering across the road, the mechanic discovered the lower wishbone mounts at the front of the car were loose, and the mountings have worn, so he is going to sort that once (if) the car ever sits level, however, the car doesn't crab or pull noticeably to one side really. Thanks again for the continued help

Varying spring pads should not be a worry, were you to go down that route. It maybe that you cannot find the root cause. That being so then playing with the pads is your answer.

Sent from my iPhone using MBClub UK
 
Some cars are a real struggle to get "right" and require lots of minor changes to become acceptable. I had a car recently that had a front track rod end, both rear leading subframe mounts, a new strut, new spheres & pipework, a new height corrector SLS valve and it still didn't drive quite right

In the end we replaced the tyres and rear ARB droplinks and suddenly it rode properly

Don't underestimate the influence of worn, hard or unsympathetic tyres. Till you fit new tyres it's not really possible to asses the way a W124 drives

I fitted Dunlop BluResponse tyres. Charles Morgan recommended them and they suit the W124 very well

Nick Froome
 
Just in way of an update, everything on the car seems to work, the ride is ok, there's no leaking sls and it raises the car when you sit three fat mechanics on the rear bumper!!!

I'm going to fit a thicker suspension pad 23mm vs 13mm, get the 4 wheel alignment checked and set up, change the tyres to Dunlop and see where that takes us

A project for further down the line is to refurbish both front and rear suspension assemblies completely, but at the moment I just need the car back on the road

Thanks for all inputs
 

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