My mechanic sent them away to Pleiadies in Queensland.   They were able to fully rebuild my rear spheres including new diaphragms, and repaint them to the factory colour and pattern.   When they arrived back they looked almost too good to put on the car!

A bit of a contrast to my front spheres.    It would only be a few years later that Citroen went to the disposable spheres.    That seems a shame, as the rebuildable spheres are still going strong 50 years later.

Fitting them is pretty straightforward, and my Mechanic had them on in a few minutes.

A quick top up of LHM later, and the DS was back to its original ride quality.   The ride is such an integral part of these cars.

The next day I took the car for a drive and confirmed everything is working properly.   The ride is back to its previous quality, and its a nice car to drive again.  The rebuilt rear spheres are doing their job well.  Since I was out on the road in the car, my Mercedes mechanic has always been interested in seeing the car, as his father had a couple of DS models in the 60s and 70s before switching to Mercedes.

I probably get more positive comments about the DS from people than any other car I own.

Of course the only downside of a drive on a Saturday morning is all the hyper aggressive cyclists. It seems once they put that lycra on, the rage builds inside. Sometimes I think they ride like they are trying to get hit, just to prove a point. Really not sure the point of cutting off cars and trying to block them on a bicycle.

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The biggest impact on ride quality is the state of the suspension spheres.   There are four suspension spheres, one for each wheel.   In addition to the suspension spheres, a D will have at least one accumulator sphere.  These store pressure for various reasons, and my car has two, a main accumulator sphere for system pressure, and a brake accumulator sphere to provide additional pressure for the brakes should there be a leak in the system or the engine cuts out.

The spheres work by having a diaphragm with nitrogen gas under pressure in the top part of the sphere, and hydraulic oil (LHM) on the other side of the diaphragm.   The compressed gas acts as the spring.    This fails to work properly if the gas pressure is not correct.   Over a period of years, the spheres gradually loose pressure.   As long as the diaphragm is still intact, the sphere can be tested and re-gassed to the correct pressure.   Eventually the diaphragm will fail and then the sphere will no longer provide any damping.    The suspension spheres on a DS can be rebuilt with a new diaphragm if needed.

This is quite a contrast to the spheres used in the Mercedes-Benz self-leveling rear suspension, which is uses the same principal.   Those spheres are disposable, and cannot even be regassed let alone totally rebuilt.   Even worse, some people simply assume that a non-punctured diaphragm means the sphere can be re-used.   Just as in a Citroen, over time they lose pressure too.

The Citroen club have regular tech days where they offer Citroen DS sphere regassing and testing.   In the roughly ten years I’ve owned the car, I’ve removed the spheres and taken them for testing to a couple of these tech days.   Last time, they were just borderline on pressure, but the Citroen DS sphere regassing system wasn’t available, so I wasn’t able to do it.

It’s not always easy for me to make the club tech days, so I enlisted the help of my mechanic for Citroen DS sphere regassing.   He first checked the rear spheres and the news was not good.  One was totally dead, with no pressure at all.  The other had a little pressure, but negligible.  These will be sent away to be rebuilt in Queensland.

The fronts were a lot better.   They had a pressure reading of around 28, when it should have been around 60.   He was able to regas these for me without issue.   He was also able to lend me two dead spheres so at least I can move the car around the garage.     I took the car on a short drive, as I wanted to do a quick oil change before putting the car away.   I did one a few months ago, but obviously didn’t seat the oil filter gasket properly, as I had a decent oil leak from the car.  Its not possible to change the filter without draining the oil.  The driving feel was quite odd.   The front being bang on spec and the rear without any give at all.

The rear spheres should be back in a few weeks.  I anticipate them transforming the ride back to what it was when I first drove the car.   It’s one of the things that makes the DS special.

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The tech day did have a hoist available, but my preference is to remove the spheres at home first.   As with last time I removed them, a strap wrench is easiest.   The spheres are different front/rear so it is important to mark where they came from on the car.

The tech day was held on the central coast, a good opportunity to take the old Pacific Highway in the 560SEC.   The car seems to be performing well after the EHA adjustment.

There was a good mix of Citroens at the tech day, including a DS, CX, and some modern Citroens.   The CX is becoming a rather rare car.   Quite a few spheres were tested, mostly the one piece units on the later models.

My spheres had readings in the low 40s for the front (42 & 45) and 28 in both the rears.   Specification for a DS front sphere is 44-64, with 59 being the ideal pressure.  Rears should be 16-28, with an ideal of 26.   I will not be able to wait another 5 years to do a sphere pressure check.  It would make sense to re-check them in another 6-12 months and potentially have the re-gassed.    I also learned a neat trick today – the plastic take away containers make great transport units for at least the single piece spheres.  I will need to check them for the rebuildable ones.

As well as doing the sphere pressure check, I also purchased 5 litres of LHM, the hydraulic oil used in the DS and other Citroens.   The Club sell it for around half the price it is available retail.

If only the hydraulic cells used in Mercedes suspension were re-gassable like the Citroen ones are!

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There are two types of spheres.   The original split type that are re-buildable, and the newer one piece type that are disposable.     You can run either type, although at least on the suspension,  the two piece type are apparently better.   Since all the accumulator is doing is providing a pressure buffer, most people use a disposable unit for this.

If you let the sphere get completely flat, the diaphragm will most likely be damaged, and the two piece spheres will need to be rebuilt (and the one piece discarded).   Therefore, it makes sense to remove the spheres every year or two and have their pressure checked and set to the correct level for the car (i.e. front and rear are different, sedans are different from wagons etc).

Citroen DS sphere removal is not particularly difficult.  To remove the suspension spheres, firstly they need to be loosened about 1/4 a turn with the suspension on high and pressurized.    This is especially important for the rear.     It is normal to use a strap wrench to do this.    It should not be particularly difficult, however on my car I found that even with a 1 metre breaker bar it was very difficult to crack the spheres.

It should not strictly be necessary, but I had to remove the air cleaner assembly to get the front sphere off.   Once the sphere have been slightly loosened then the car needs to be set to the lowest suspension setting and the system pressure released via the screw on the side of the pressure regulator.     Once this is done the spheres can be removed by hand, with something to catch the hydraulic fluid that will spill.

The spheres for the front and rear have different pressures, so it is important to make sure that the spheres are not mixed up.

I had also wanted to replace the accumulator sphere, and replace it.   My hydraulic pump needs to kick in every 5-10 seconds.   This could be because the accumulator is flat and not holding pressure.  It also could be an internal leak in one of the other hydraulic components such as the centrifugal regulator, or the steering rack.    Since my accumulator is the disposable type, and I had purchased a replacement, I wanted to change it. Citroen DS sphere removal may be easy for the suspension, but this is not the case for the accumulator.

However, despite breaking a chain wrench, I was unable to remove the accumulator.   I will likely have to remove the entire pressure regulator assembly, which is quite fiddly as all the hydraulic lines need to be removed and new seals fitted.    Something for another day.

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