rear suspension spheres on W124 estates


MB Enthusiast
Apr 23, 2003
Bexhill, East sussex
Alfa GTV 3.0
Here's a sort of "how to" replace the rear spring accumulators on W124 estates - this method was worked out by a matter of trial and error - mostly error but may well help other people who are faced with replacing the spheres.

if you are thinking of attacking the job, there are 2 ways to do it, one is the "proper way" which Mercedes book at 5 1/2 hours labour but realistically for the home mechanic will take longer as there are a couple of "special tools" required to do it this way

secondly and in real terms much quicker is to do it the way I ended up doing it and assuming you don't need to grind the old nuts off should take no more than two to three hours actual work.

Parts you will need

2 x suspension spheres - cost about £140 the pair

2 x rubber seals - they sit on the base of the spheres and seal the bodywork - cost pennies

2 x new hydraulic pipes to connect the levelling unit to the spheres - cost about £12 the pair - don't try and make your own there is an insert in them that is designed to slow the flow of fluid

1 x new bracket for the self levelling unit - you may not need this but best to be prepared - cost about £5

4 x 16mm copper compression washers - cost pennies

6 x 10mm nyloc nuts

2 x 1.5 cm m6 (I think) metric fine thread bolts and a tube of loctite

2 litres of MB hydraulic Oil - ZHM fluid - cost about £17

tools required,

axle stands

torque wrench

10mm hex key (preferably socket driven as you need to torque use a specific torque)

11mm socket - to remove the remains of the old unions

11mm spanner - to re tighten the hydraulic unions

10 mm socket with a pretty narrow wall on the socket side to remove the retaining nuts for the spheres

10 mm open ended spanner to detach the self levelling unit

10" extension drive

3" waggle joint extension bar or universal joint extension


chisel :)

cross head screwdriver

optional tool - power drill with mini grinding wheel/attachment or a dremel grinder

rough work plan (isn't hindsight a wonderful thing?)

1, remove the floor section immediatle behind the rear seats - it's held in with 6 cross head screws. lift it from the middle quite firmly - it may seem like it doesn't want to give but it will - it may bend slightly as it's only thin steel but it's easy to straighten

2, with the car up on axle stands attempt to loosen the 6 x 10 mm bolts that hold the spheres in place - don't take all of them right off - you just want to loosen them at this stage to make sure they will move. If they don't or the captive bolt breaks loose - like 3 of mine did you'll need to grind them off from underneath the car once you have detached the hydraulic pipes

3, remove the two bolts that hold the levelling unit in place - the top one is a swine to get at as it is behind hydraulic pipes.

4, place a large bowl under the car and loosen the passenger side banjo union on the base of the sphere (10mm hex key). Let the oil drain into the bowl - you are going to get wet here as you are releasing pressure on the system so do it carefully and when the car is cold - that oil gets bloody hot!!!!!! The "official" method is to attach a pipe to then loosen the screw on top of the self levelling unit to drain the fluid - you'll see why this "alternative" method is easier once you get under the car :)

5, now repeat that on the other side - do not bend the large pipes out of the way even though it's tempting as it will cause you problems on reassembly (don't ask)

6, when the oil has stopped dripping chisel the unions for the small bore hydraulic pipes off flush with the old spheres and cut them with pliers at the levelling unit, remove the unions from the levelling unit using an 11mm socket and plug the holes to stop any drips - the new spheres you have bought will have plugs in that you can use for this purpose. Pull out the remains of the hydraulic pies and after noting which way they fit throw them away

7, now you can remove the spheres, if the come out easily great - if not be prepared for some awkward grinding of the nuts.

Once they are out, the bracket for the self levelling unit will be freed, so throw that away :)

If you've got the time to spare I'd take the car off it's jacks/axle stands and leave it overnight at this point with a bowl under the self levelling unit, remove the plugs and let the rest of the oil drip out - it seems to be the most effective way of draining the system completely. Bear in mind that with no pressure at all in the system the car will sit very low on the rear springs whan you remove the jack so don't use a bowl that is too deep

Reassembly is the reverse, put the spheres and the new bracket in and fix them with the 10mm nylocs - torque up to 20 nm

fix the self levelling unit to the new bracket with the small loctited bolts.

connect the shorter of the two new small bore hydraulic pipes to the drivers side sphere and the levelling unit first - you'll see why

then connect the feed to the passenger side.

Connect the banjo unions to the base of the spheres using a copper washer on either side of it and torque up the hex bolts to 30nm - do not try and go any higher!!!!!!!!! and be very careful not to cross thread them - it's far too easy as the spheres are very soft metal - if you do cross thread them you'll need a 16mm metric fine tap to clean the thread (once again don't ask).

With that complete, let the car back down onto the ground and fill the reservoir with oil - you will need about 1 litre initially.

Make sure the screw top is on the reservoir but leave the filler hole open, load the boot - you need a weight of at least 120kg to set it up right so a couple of friends sat in the back is perfect. Get someone to start the car and hold the revs at 2000 for about a minute whilst the suspension rises and add the rest of the hydraulic fluid as required. Once the level of the car and the fluid has stabilised, switch off, unload the car and start it again to check that the levels are fine.

Check for any leaks, take for a test drive and marvel at how smooth the car now feels.....

these spheres have a "life" of about 100,000 miles and if your rear suspension feels harsh or lacks damping they are the most likely source of the problem.

Dispose of the old spheres carefully - before throwing them away you should drill a 3mm hole in the top of them to release any residual pressure/gasses - wear goggles and drill slowly with a lubricated drill bit.

Last edited:


New Member
Oct 1, 2005
Telford Shropshire
1992 190E
muchas gracias

Couldn't have asked for a more comprehensive reply. Thanks a bunch Andy. I'll buy you a drink or two when your in spain.
Got little or no help from the benzworld site.
Looks like I've got a full weekends work.
Better make a start.

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