450SEL (4.5Ltr) Rear Only Self Leveling Suspension - advice sought

Started by goldacre, 26 February 2022, 08:57 AM


Hi folks, before i proceed, yes i did search the Forum but came up short :/

So, my rear only SLS cannot get it up :( when searching i found a post that said if the spheres let go (and mine are 15+ years old) it wont respond. Checked oil flow and it circulating (but no pressure test done, can this be done?) no leaks in struts (thank God...) leveling device looks in good order.


1) what is the colored dots for the rear only SLS?
2) what are the part numbers?
3) can other spheres be interchanged for my cars system (i posted back in 2011 when i received spheres that were not correct for my car, Tom Hanson explained the difference...) donated them to TJ450s 560SEL as he has helped me out heaps...)
4) does anybody have any for sale NOS or equivalent? have a quote off MB Classic Center but thought i would hang my hat out, just in case...

Many thanks in advance :)

12/1979 450 SEL 148K on clock (museum piece)
12/1986 Lotus Esprit Turbo 87K on clock 'Darling, look what Q has brought for us, isn't it nice' :)


From my experience with the 6.9 spheres going bad will not cause it to not pump up.  If your spheres are that old then for sure they need to be swapped out yes.  Likely your issue is in the leveling valve.  Any debris can cause a check valve not to seat.  I would suggest a full fluid flush with filter change and new spheres for openers.
The rears on the 6.9 are the green dot ones, likely same for yours but best to check EPC.
1977 450 SEL 6.9 - Astralsilber


Raising a hydro system I found that if the car is too low then the leveling valve is not in the range where it can fill the system.  Combinations of jacking the car up to ride height and lowering can help get the fluid flowing correctly.
'68 250S
'77 6.9 Euro
'91 300SE,
'98 SL500
'14 CLS550,


Cheers guys, will have a crack at playing with leveling valve, i see it has adjustment and if adjusted and working should do something but before that will try lifting car up and see what happens, guess this is done with motor running? Will do sphere replacement and filter, i have the correct fluid and it matches what is in the reservoir, its definitely not auto trans fluid  8)

Is the leveling valve serviceable? Parts available? can it be removed and cleaned up? has anyone done this?

I did look at a air bag system on the market, they said its a direct replacement but need to manually adjust ride height with switches operating a compressor and pressure tank, definitely a last resort  ???

12/1979 450 SEL 148K on clock (museum piece)
12/1986 Lotus Esprit Turbo 87K on clock 'Darling, look what Q has brought for us, isn't it nice' :)


I'm not familiar with the rear-only leveling system, but assume that it closely resembles the rear of the 6.9.  If so, you can do some experimentation with the valve by removing the lever arm from the valve and moving it by hand.  It's quite likely that removing it will destroy the plastic ball sockets, they embrittle with age, so order a replacement beforehand.  They're available and pretty cheap.  Good luck and cheers, 
Now:  1976 6.9 Euro, 2015 GL550
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0


Cheers raueda1,

that might be a way to go after the jacking up of the car to see if anything happens, could mean crap in the system has blocked a few components, just hope its serviceable when taking apart, the rear sightly looks lower than the front when idle but when you put people in it squats down even further :/ will place the plastic coupler on the shopping list, it may already be broken, need to take a closer look.

the 6.9 Vs rear only SLS when searching was all about the 6.9, could not find a supplement for the rear only SLS (the library on the 6.9 suspension is HIGE, could of missed it if a one pager of the whole omnibus of info). My only knowledge of it is i  recall hearing the spheres are a different colored Dot to what ios used on the 6.9, just cant remember which color :/

12/1979 450 SEL 148K on clock (museum piece)
12/1986 Lotus Esprit Turbo 87K on clock 'Darling, look what Q has brought for us, isn't it nice' :)