Post
by Dieselman » Sat Apr 22, 2023 6:53 am
It looks like Gasa only removed both rear bolts, rather than the Lh ones.
I'm surprised it created enough room to remove the anti-sink sphere, but obviously it did. It might be a simpler method, as these bolts are extremely easy to access.
Citroen call this sphere the Smac sphere and refer to it as anti sink We had some debate as to it's actual purpose and it appears it is there to provide reserve rear brake pressure in the case of pump/main circuit failure.
With Smac, the anti-sink valve isolates the rear hydraulic rams when main circuit pressure falls, with the theory being the rear brakes can no longer use the rear suspension to provide the required pressurised fluid, thus a reserve sphere was added.
The anti-sink (reserve rear brake pressure) sphere and the centre hydractive spheres are often neglected, as the owner doesn't feel a direct influence so leaves them.
Citroen drivers are not alone, many Mercedes Sls and Abc system spheres are left until they rupture.
If you are not familiar with the Mercedes systems, they are similar to the Citroen system, but because of patent restrictions, the cars don't ride on the hydraulics using the spheres as the suspension springs.
In the case of Sls (self levelling suspension), the car rides on coil springs and the hydraulics provide additional assistance when the rear of the car drops under load and additionally the spheres act as the dampers.
In the case of Abc, the car rides on coil springs inside the strut unit and the hydraulic pressure is used to adjust the ride height at each corner individually, via an electrovalve pair for each corner. One valve is an isolator valve (anti-sink), one valve is height correction (fluid admittance/hold/withdraw).
This makes the system very similar to the Citroen Hydractive 3+ used on C5 and C6, with the exception that the Mercedes spheres are simply accumulators, a larger one for the pressurised feed, a smaller one for the return, to act as a pulsation damper.
I suspect lack of accumulator sphere maintenance might contribute to hydraulic strut failure on these systems, as the shock loading of the rams will be significant, whenever the elctrovalves are open, due to the lack of accumulator gas pressure. This will be a considerable time as the body height is being constantly controlled to stop squat, dive and roll.
The citroen Hydractive3+ system doesn't incorporate anti-roll, but does have variable rate spring and damper setup, as all Hydractive systems do.
The system is fully electronic with no mechanical height correctors, as fitted to Hydractive1 and Hydractive2 systems, but is otherwise very similar, except having a pair of spheres for each wheel, instead of each axle sharing the hydractive sphere.
Apologies for topic drift, Gasa.
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