Centre front sphere from the XM model.

[Turbo Killer]

My BX is sinking at the rear quite quickly when the engine is off and i am only getting about 10 seconds between clicks, i've looked through the service history and i can't find any record of the accumulator sphere being changed, so i am going to change this first and see how it goes, i have read the FAQ section about changing spheres and one of the tips for the accumulator sphere is a centre front sphere from the XM model, is this also an accumulator sphere, i just want to get it right for when i order one, also who do you guys recommend for parts?

Just had another flick through the history, the sphere was replaced in 1997.

[rayfenwick]

Hi there

The XM centre spheres are not accumulators - they're suspension spheres, similar to the corner ones in their specification. The XM does, of course, have an accumulator sphere, and later S2 cars have an "antisink" sphere as well, bringing the total to 8.

CX's have 6, 4 corners, accumulator and a separate brake accumulator.

With regard to swapping spheres, there are 2 camps: those that experiment, and those that leave well alone. There are respected and knowledgeable people in both camps. I've not heard of swapping the BX accumulator for an XM sphere, but that doesn't mean much...

I too am interested to hear from more knowledgeable people on this.

[MULLEY]

I think the reason is that the xm sphere is a higher capacity sphere than the bx one, so it should last longer? possibly it makes the suspension nicer overall?

[rayfenwick]

Perhaps, but AIUI there's no damping on an accumulator sphere, whereas suspension spheres are damped. A suspension sphere might not let pressure out quickly enough for some situations.

As I said, I'm no expert by any stretch of the imagination, and I'd gladly be corrected by someone who knows better.

[Defender110]

Yes I read the same advice (on Citroen DIY I think) changed my old TDG Turbo accumalator sphere for an XM accumulator sphere when I had very bad tick times and it increased it dramatically 30 seconds IIRC.

[RxBX]

............ i have read the FAQ section about changing spheres and one of the tips for the accumulator sphere is a centre front sphere from the XM model, is this also an accumulator sphere,....

Hi 'TK',
The accumulator sphere is the same for the BX/XM/Xantia (62 Bar), the only better ones that where fitted to an XM was the ones sometimes called a Euro-sphere as these had the triple diaphragm/membrane's fitted which where identified by three dimple's in the surface of the metal sphere just around the nitrogen charging port (The opposite end to the screwed connection), but this type of sphere does not tend to be supplied by after market supplier's even for the XM model's but just the standard single diaghpram type !

The centre spheres as used on an XM for the Front is pressured to 72 Bar (Although the table states 70 Bar) also note that it has a bigger volume than the Accumulator and the Rear ones are pressured to 50 Bar.

So basically, apart from the volume on the XM front Hydro-active centre sphere the accumulator and the XM centre sphere's are identical apart from what actual Nitrogen pressure the sphere's have been charged to !

This sphere application TABLE will clarify the sphere volume/pressure/damper size (Note! Accumulator spheres do not have dampers) also the Citroen/Amtex parts numbers are given so you should be able to get the Amtex ones from your nearest GSF outlet !

Do forget to use your 10% BXC discount after they've quoted/committed a price to you

I hope this maybe of help for you/others.

[Defender110]

I hope this maybe of help for you/others.

It certainly is, thanks Rick

[Turbo Killer]

............ i have read the FAQ section about changing spheres and one of the tips for the accumulator sphere is a centre front sphere from the XM model, is this also an accumulator sphere,....

Hi 'TK',
The accumulator sphere is the same for the BX/XM/Xantia (62 Bar), the only better ones that where fitted to an XM was the ones sometimes called a Euro-sphere as these had the triple diaphragm/membrane's fitted which where identified by three dimple's in the surface of the metal sphere just around the nitrogen charging port (The opposite end to the screwed connection), but this type of sphere does not tend to be supplied by after market supplier's even for the XM model's but just the standard single diaghpram type !

The centre spheres as used on an XM for the Front is pressured to 72 Bar (Although the table states 70 Bar) also note that it has a bigger volume than the Accumulator and the Rear ones are pressured to 50 Bar.

So basically, apart from the volume on the XM front Hydro-active centre sphere the accumulator and the XM centre sphere's are identical apart from what actual Nitrogen pressure the sphere's have been charged to !

This sphere application TABLE will clarify the sphere volume/pressure/damper size (Note! Accumulator spheres do not have dampers) also the Citroën/Amtex parts numbers are given so you should be able to get the Amtex ones from your nearest GSF outlet !

Do forget to use your 10% BXC discount after they've quoted/committed a price to you

I hope this maybe of help for you/others.

Cheers for the information, very useful table.

Is there any detriment to the system if a sphere with a damper is used for an accumulator?

[RxBX]

............................
Is there any detriment to the system if a sphere with a damper is used for an accumulator?

In a nut-shell DO-NOT fit a sphere with a damper fitted in lieu of an accumulator type !

It would be like fitting a flat sphere (Even if the sphere is new), just take a look at the sphere without a damper, it's orifice/opening goes from approx. 25mm bore at the neck/opening and then in the bottom of the bore it taper down to a hole approx. 3mm in diameter, (Take a look at THIS post/thread for example/photo's on Club-XM.com site) !

If you have a good accumulator type sphere, which you are looking at you can just see the diaphragm/membrane on the other side of the hole (the inner side of the sphere) so basically that is the first contact point for the LHM fluid which helps to keep the rest of the hydraulic system up to the correct working pressure with an instant when the system requires it !

So just imagine what effect a sphere (fitted on a vehicle in lieu of an accumulator type) would have when fitted with a damper with a bore dia. as little as 0.5mm restricting the flow of LHM fluid even before it enters or escapes thro' the larger (3mm hole in the base of the neck), so I'm sure you really don't need any explanation of the consequences ?

Also running a hydraulic Citroen with a flat Accumulator sphere will put extra load on the rest of the hydraulic system and HP pump under stress, which WILL ultimately lead to the the rupture of the steel pipe from the HP pump and the pressure regulator with the loss of most of the LHM in the reservoir and could leave stranded with no hydraulics to support your suspension, PAS (If fitted) and most important your brakes

Read THIS to understand the importance of the accumulator sphere !

Or thro' ALL the sections, it may help you understand the hydraulics on Citroen vehicles better, if you just want to get to the BX ref. click HERE !

Happy reading/enjoy.

[Turbo Killer]

Cheers RxBx, excellent information

I have some spare time next week and I'll be fitting a new accumulator.

[MULLEY]

I'd personally get one from Westroen, great service & price isn't that much more than GSF & it comes with a 3yr warranty rather than the poxy 1yr that comes as standard unless spending mega bucks on a citroen original & even they only come with a 2yr guarantee.

[rayfenwick]

In a nut-shell DO-NOT fit a sphere with a damper fitted in lieu of an accumulator type !.....It would be like fitting a flat sphere.... so I'm sure you really don't need any explanation of the consequences ?

Glad to have that confirmed Richard. Being quite green to the ways of hydraulic Citroens (oh, the punnage!), I'd worked out that an accumulator sphere definitely didn't need damping -it would be contrary to the rationale of the accumulator sphere - perhaps I'm not as clueless as I fear?