HOW TO MAINTAIN AND CHANGE YOUR CITROEN SPHERES??

What is a sphere / hydraulic suspension ?

The hydraulic suspension, (or hydropneumatic suspension), is an invention generated by Citroën, just after the war, equipping approximately 9 million vehicles from 1954 to 2017. With a few exceptions, (Rolls Royce Silver Shadow, Peugeot 405 x4, or Mercedes 450 SEL 6.9) all models carry Citroën badges. Derived from the "oleopneumatic suspension" created in 1925, this new system was innovated on the rear axle of the Traction 15-six H in 1954. But it will be put forward and marketed from 1955, thanks to the Citroën DS (and coupled to the power steering, moreover)! It will then be placed as standard on the CITROËN AX, BX, C25, GS, C5, C6, SM, Xantia and XM.

There are 3 kinds of particularities for the spheres:

- The green spheres, called "classic" for non-hydractive suspension systems" divided into 2 kinds: Those called "stamped", whose two half-spheres are welded, and those called "screwed", like on the Citroën DS for example.

- And the gray spheres called "saucers" for the Xantia and XM HYDRACTIVES, the latest generation of spheres, fitted to the most recent vehicles.

Abandoned in 2015 for a question of cost, the concept of hydraulic suspension will be taken up in 2017 by AUDI and MERCEDES for several of their models.

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What is a hydraulic sphere used for ?

The role of a CITROEN sphere is to filter and dampen the irregularities of the road, for better driving comfort. The hydraulic system to ensure stable support, regardless of road conditions.

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How do the spheres work on a CITROEN Xantia or a C5?

The motor drives a high pressure pump coupled to an accumulator, which is responsible for distributing the hydraulic fluid (LHM, LDS, etc.) under high pressure in the various systems, such as braking, steering assistance, etc.

The axle rests on a piston which slides in a cylinder coupled to the ram. This cylinder is made of high-pressure oil, and it is therefore overhung by the sphere. This sphere is separated into two parts by an extremely resistant deformable elastomer membrane. The upper part of the sphere is filled with nitrogen (non-toxic and non-flammable gas), and the lower part is filled with LHM oil. These two compartments are waterproof. An orifice equipped with valves in the bottom of the sphere allows the passage of oil through the cylinder, up to the jack.

When you start your Citroën, the oil is under pressure, thanks to the pump. It then puts pressure on the membrane and compresses the nitrogen until a perfect balance is reached. Once underway, the nitrogen pushes the LHM back, which returns the suspension arms (via the piston) to their starting position. At each pothole, or at each bump, the sphere can withstand up to 200 bars of pressure. The LHM itself supports a pressure of approximately 150 bars throughout the car's hydraulic circuit (mainly at the pistons). When the suspension sinks due to the compression of the gas, the cylinder fills with hydraulic fluid, thus maintaining a constant balance. The road holding of the vehicle is amplified and the comfort remains of high quality.

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What is the hydractive system for xantia and xm?

This complex system cannot be described in a few lines, nor restricted to a paragraph. That's why we dedicated a whole article to it! Consult now our information page on the operation of the Citroen hydractive system.

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When and how do I maintain the hydraulic system of my CITROEN C5 / Xantia? :

LMH liquid:

It is important to ensure that impurities do not enter the system. Therefore, to avoid fatal fouling, you must regularly:
- Drain and renew your hydraulic fluid approximately every 30,000 km.

- Clean the LHM tank filters.

- Do not forget to bleed the braking system approximately every 2 years.

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The spheres:

- It is necessary to change, at least, the pair of front or rear spheres, as well as the accumulator.
- Always replace the spheres with the reference that corresponds to the vehicle. Even if their calibration is identical, two spheres with different references will be fundamentally discordant and will not have the same impact in your car.
- Always place the O-ring in its housing, on the cylinder. Never place it directly
on the sphere.
- Purge the circuit each time you replace the spheres.

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What are the problems with the suspension system? How to know if the spheres are to be changed?

What are the most common flaws of spheres?

- Hardness of the suspension: due to the natural deterioration of the sphere. The porosity of the membrane facing the nitrogen molecules causes a loss of pressure, and it eventually ruptures. In this case, it is possible that the gas comes out of the circuit, replaced by the LHM which takes the place... but does not compress!
Then you have to purge everything.
- Floating suspension: due to the presence of air bubbles in the circuit or valve wear
of the sphere. Do not hesitate to check the pressure of your spheres.

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Problems arising from other elements of the suspension system preventing the proper functioning of the spheres:

- Faults located in the pressure pump, steering, suspension or brakes, caused by
impurities in the circuit.

- Defective or worn seal: fluid leakage.
- Cylinder defective, seized or leaking oil.
- Operating problem in the rear suspension arm or in the trapezoids
before. This causes the harshness of the suspension.
- Faulty height corrector.
- Brake distributor out of order causing excessive sag.

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HOW TO REPLACE / CHANGE THE SPHERES ON A CITROEN BX / CX?

To replace your spheres, you will need a chain wrench (left illustration), or a strap wrench (right illustration), to make the process easier.

You will also need new LHM, clean rags and a size 12 spanner!

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Dismantle the spheres:

First: Release the pressure:
- Start the engine.
- Place the height control in the high position then in the low position to depressurize.
- Stop the engine.
- Get out of the car leaving the driver's door open.
- Loosen the bleed screw without removing it completely so as not to lose the sealing ball.
- Wait for the loss of circuit pressure.

Then: Remove the damaged sphere.
- Once the pressure is released, loosen the sphere (this should be done easily). If it is blocked,
this means that there is still pressure: PARTIALLY loosen the pressure relief screw of the contactor-circuit breaker with your 12 wrench. This screw holds a ball which manages the opening of the circuit, allowing the pressure to escape into the return circuit.
- Sometimes, the sphere must clamp on a plate support.
• SC/MAC rear axle (regulators)
• SC.CAR under the gearbox
In this case, the supply pipe must be uncoupled before unlocking the sphere.

- Place the rags under the sphere, which will be emptied of LHM when disassembled.

- Use your chain or strap wrench to unscrew the old sphere.

USEFUL NOTE: For the front suspension spheres, the car must be in the low position. For the rear suspension spheres, it is better to have the high position, to block the cylinder completely).

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Move up the spheres:

Then, Place the new sphere
- Seals and interior parts must be wetted with LHM hydraulic fluid.
- Replace worn seals with new ones. They are generally supplied with the spheres.
- On the cylinder, place the O-ring in its housing (never place it directly on the screw
of the sphere). Then mount the new sphere and tighten by hand (and only by hand!).
- Couple the supply pipe if the sphere is clamped on a plate support.

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Purging the circuit:

Finally, bleed the suspension circuit.
- Fill with LHM up to the level mentioned.
- Start the engine.
- Loosen and tighten the contactor-circuit breaker bleed screw several times.
- Place the manual height control in the high position.
- Check the LHM level.
- Top up the level with the engine running, if necessary.
- Switch off the engine.

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CAN WE RIDE WITH DEAD SPHERES ?

Only time to receive the news, or to go to your garage. Indeed, the absence of a shock absorber process on your car will harm a good number of mechanical parts, which are badly abused by your journeys, and you risk having it for much more than a simple change of spheres.

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DO YOU NEED TO CHANGE ALL THE SPHERES AT ONCE ?

This question is debated in the spherical world. Some will say that it is enough to change the worn spheres, or even to rehabilitate them, without touching the others. To reduce the cost at the moment.
We believe that changing them partially one after the other will have a cyclical effect on your hydraulic system. The remaining spheres will drop one after the other, weakening each time a little + the hydraulic circuit and the adjacent parts (braking, power steering, etc.).

At sphere-discount.com, we advise you to change all the spheres at the same time. And to purge the entire circuit at once, to be quiet for several years without worries!