124 estate; partial collapse of SLS

[mattc]

Rear nearside suspension collapses when engine is off. Rises when driving along and collapses so the arch is about an inch above the wheel when I turn engine off.

Have been under the car this morning and can see no evidence of leaks from the hydraulic struts or the accompanying pipework. the level control unit looks fine too. Cannot really see what is happening with the accumulator spheres.

Before I simply go sourcing spares to change does anyone have any ideas?

I confess the reservoir is slightly under the min (which has been the case ever since I refilled the system after repairing a section of the SLS a few months ago) but it was working fine and holding the car up until a few days ago.

 

[SilverSaloon]

have you checked the spring? i thought the height of the car was purley determined by the spring once the engine is off.

 

[mattc]

Spring 'looks' fine but who can I tell short of taking them out both?

Dont the hydraulic struts help hold the car up normally anyway? You dont see all s124's saging at the back when engines are switched off like Citroens of old

 

[SilverSaloon]

Spring 'looks' fine but who can I tell short of taking them out both?

Dont the hydraulic struts help hold the car up normally anyway? You dont see all s124's saging at the back when engines are switched off like Citroens of old

i think there was a good explanation on a thread here about how it worked but cant find it now....

 

[Will]

If there's no leaks (would be obvious from underneath ) I'd say it looks like the levelling valve is playing up. Once the pipework from the valve to the accumulator/strut is filled with fluid, it should stay there until the valve is opened again. Hence if the level is dropping, the fluid will be going somewhere - back past the valve I suspect.

Will

 

[moakesr]

If there's no leaks (would be obvious from underneath ) I'd say it looks like the levelling valve is playing up. Once the pipework from the valve to the accumulator/strut is filled with fluid, it should stay there until the valve is opened again. Hence if the level is dropping, the fluid will be going somewhere - back past the valve I suspect.

Will

Will is correct, the self levelling valve controls fluid return, however I would expect both sides to fall and rise together?

 

[SilverSaloon]

this thread seems to cover a lot of faults and solutions to the SLS. Post 3 especially

http://www.mbclub.co.uk/forums/engi...ump-95-w124-estate-need-part-number-part.html

2, the car's rear drops when you leave it parked - self levelling valve knackered or in need of an overhaul. The non return part of the valve is no more complicated than a spring and a ball bearing, sometimes just giving the valve a tap can fix it

 

[mattc]

Thanks for the pointers

So how do i check if the level control unit has failed??

Mention is made of the system typically collapsing on both sides when this part fails...which suggests there is only one non-return valve...but mine has only collapsed on the one side suggesting each side has an individual non-return valve. Does anyone know for sure whether the part has one or multiple valves? or are the valves in the pipework/connectors attaching to the unit?

 

[andy_k]

I suspect the strut is leaking internally.

If the Self levelling valve was leaking both sides drop like an old Citroen - our old red estate had that problem.

The valve is located on the drivers side, behind the rear wheel

The springs do not support the full weight of the estate cars, we've had this discussion before and with no fluid pressure they drop like Matt has described.

 

[mattc]

I suspect the strut is leaking internally.

Ahhh, so the fluid is not being lost; simply leaking AROUND the closed system when it should not be! Eureka I hope - will get on with sourcing a strut either locally or fleabay...unless anyone just happens to have one lying around they want to sell?

 

[moakesr]

I suspect the strut is leaking internally.

If the Self levelling valve was leaking both sides drop like an old Citroen - our old red estate had that problem.

The valve is located on the drivers side, behind the rear wheel

The springs do not support the full weight of the estate cars, we've had this discussion before and with no fluid pressure they drop like Matt has described.

I think Andy is spot on with this, I wanted to say this with my last post, but couldn't quite convince myself. Fluid must be leaking past the piston seal in the strut body. No external leaks, but sinks when parked.

 

[Will]

I think Andy is spot on with this, I wanted to say this with my last post, but couldn't quite convince myself. Fluid must be leaking past the piston seal in the strut body. No external leaks, but sinks when parked.

I do like the idea behind this logic, seem plausable etc. But I can't quite get my head around the strut leaking internally. What I mean is, if the fluid is seeping past the piston seal, won't it be making it's way outside of the strut?

Will

 

[Ian B Walker]

I do like the idea behind this logic, seem plausable etc. But I can't quite get my head around the strut leaking internally. What I mean is, if the fluid is seeping past the piston seal, won't it be making it's way outside of the strut?

Will

No it will be recirculating within the strut tube.

 

[Number_Cruncher]

I don't *think* there are any valves between the S1 and S2 ports on the level control valve - which means the static pressure in the LH and RH suspensions are the same.

Therefore, if one side sags, and the other doesn't, I would look for mechanical cuases like damaged springs first - I don't think this is an SLS fault.

 

[mattc]

Should update you all on this. Having done nothing for a week I drove it a few days ago for a few miles. System pumped up the collapsed side and it has stayed up since then. I have done a trip of 150 miles with a washing machine, bookcase, and assorted stuff with no ill-effect. Go figure what happened there then?

long live the 124!

 

[219]

If fluid was leaking back past the valve , you would see the level increase in the reservoir under the bonnet (marked Hydraulik Oel ZHM) .

Otherwise , I'd agree the most likely causes are either a broken spring ( should be visible on inspection ( jack the car up and remove the wheel ) or , most likely an internal leak in the strut which would not affect the other side . New struts not cheap , alas .