Changing Spheres

Frequently asked technical questions and common modifications/improvements
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mat_fenwick
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Changing Spheres

Post by mat_fenwick » Tue Dec 15, 2009 5:05 pm

Given sensible caution, is its very easy to change any of the spheres on your BX without enlisting the help of a garage.

But two very important things

1) System pressure is around 2000psi, and unscrewing a sphere without depressurising the system could result in serious injury or death!

2) A car suddenly depressurising could drop immediately and kill you, the car MUST be supported!


Ok, there's the warnings out of the way. We're now going to show you how to change spheres without injuring yourself and in a short time whilst saving yourself £'s.

Accumulator Sphere

What is it for?
The accumulator stores system pressure to be used by the Brakes and suspension. It has a gas volume of 62 bar.If the accumulator is "flat" (i.e. as a result of nitrogen gas gradually escaping from it over a period of time) the result is the the Hydraulic Pump must work very hard to maintain system pressure. When this sphere is flat you will here a frequent ticking or clacking as the pressure regulator opens and shuts rapidly. This is very undesirable. The accumulator stores pressure to give the pump an easier life, it also holds a reserve of pressure in case of hydraulic failure, giving some braking and suspension pressure for a short time should the pump fail.
It is therefore vital that a new accumulator is fitted should you here the "clacking" in an interval of less than 15 seconds between clicks. A new accumulator will only allow the regulator to open close maybe every 30 seconds providing that the HP pump is sound.

Where do I find it?
Its a green sphere screwed onto the Pressure Regulator which is mounted on the front of the gearbox bellhousing, behind the radiator.

Changing the Accumulator
Run engine and place height lever into "high" position. Place trolley jack under front subframe, jack up car, them place axle stands under front subframe either side.
Turn off engine and move height lever all the way forward into Low. Then open the 12mm bleed on the pressure regulator 1/2 a turn to release any remaining system pressure. Wait 5 minutes.
Using sphere removal tool loosen accumulator sphere, remove tool and unscrew by hand. Have a bucket handy to catch any split LHM fluid. If you don't have a sphere tool, the accumulator can be tapped loose by using a chisel and hammer to rotate it in an anti-clockwise direction.
Remove the old sphere seal from the regulator and carefully fit the new one provided with the new accumulator so that its flush with the pressure regulator body. Screw on the new accumulator in a clockwise direction. Tighten just over hand pressure.
Start up the car with the height lever in the HIGH position, and open the 12mm bleed valve 1/2 turn, and let engine run for 20 seconds. Tighten valve. Then open and close valve 1/4 turn 10 times, and retighten. Car should now rise to "High" at the back. Remove axle stands, and jack carefully. With car running in high, check LHM level and top up if required.

Our handy Tip!
Some of us have replaced the standard accumulator with a centre front sphere from the XM model. This has greater pressure (70 bar instead of 62) and may help if your car has a slightly weak pump.

The Front Suspension Spheres

What they're for

The front spheres act as shock absorbers do on a "normal" car. The difference is that the sphere is a metal ball, inside the top half is filled with Nitrogen gas, then there is a plastic membrane. The bottom of the sphere contains LHM mineral fluid. When the car crosses a bump, the front arm is pushed up, this in turn pushes upwards the piston in the front strut which forces LHM into the sphere. This moves the sphere membrane up against the nitrogen to produce the Damping effect.

Where do I find them?
Under the bonnet, either side of the inner wings!

Changing the front Spheres.
Good News! This is a nice easy one. There's no need for a jack and the front spheres come off easily. With the car in the High position, and the engine off, loosen both front spheres no more than 1/4 turn using the sphere tool, or a chain wrench. Place the height lever in the Low position, and allow 5 minutes for pressure to release. Remove both spheres using hand pressure anti clockwise. Use rags to mop up any LHM that will spill onto the inner wings. Remove the old sphere seals from the top strut mounts.

Fit new sphere seals into top strut mounts flush, then screw on both new front spheres just over hand pressure. Start the car and place lever into High position and check LHM level, top up if required. Move the height lever slowly from High to Low with interval of a minute in between to bleed the system 4 or 5 times

The Rear Suspension Spheres

What they're for

The rear spheres act as shock absorbers do on a "normal" car. The difference is that the sphere is a metal ball, inside the top half is filled with Nitrogen gas, then there is a plastic membrane. The bottom of the sphere contains LHM mineral fluid. When the car crosses a bump, the piston in the rear arm is pushed up, this in turn h forces LHM into the sphere. This moves the sphere membrane up against the nitrogen to produce the Damping effect.

Where do I find them?
Underneath the back of the car at either side, mounted on the rear struts horizontally..

Changing the Rear Spheres.
Bad News! This job is not so easy as the front ones, but, its OK. With the car in the High position, and the engine off, jack up both sides of the rear of the car and place 2 axle stands securely under the rear axle tube, lower jack so that the car is supported by the axle stands, and check that all is safe. On no account should you attempt to loosen the spheres in "low" as the strut will twist, fracturing the hydraulic supply pipe! Loosen both rear spheres no more than 1/4 turn using the sphere tool, or a chain wrench. The rear spheres may be "tight" due to corrosion. You can try and loosen them using a cold chisel and a hammer, with great care, but the proper sphere tool, with gentle taps from a hammer is the best bet. Place the height lever in the Low position, and allow 5 minutes for pressure to release. Remove both spheres using hand pressure anti clockwise. Use rags to mop up any LHM that will spill onto the ground. Remove the old sphere seals from the strut mounts.

Fit new sphere seals into strut opening so that they sit flush, then screw on both new rear spheres using just over hand pressure. Start the car and place lever into High position and check LHM level, top up if required. Move the height lever slowly from High to Low with interval of a minute in between to bleed the system 4 or 5 times. In the case of the rear spheres I also bleed the system at the Pressure regulator by opening and closing the 12mm valve 1/4 turn a few times with the car running, and in "high".

Don't forget to check and if required top up the LHM level.

Thanks to Jon Wood for the write up.

EDIT - If the diaphragm inside the sphere has ruptured (noted by no springing at that corner) then the nitrogen which was contained in the sphere will be pressuring the LHM still, even with system pressure released. This can be felt as the sphere will be 'tight' to unscrew all the way to the end of the thread, rather than cracking off and unscrewing freely. If this is the case, then move your face out of the way as you get to the end of the thread, as pressure will suddenly be released accompanied by a spurt of LHM.
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1993 1.9 TZD Turbo Estate
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1985 Hyundai Stellar V8
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Post by robt » Fri Oct 14, 2011 12:07 am

The accumulator is on my jobs list, so I've printed off this useful thread :)

Can someone confirm that I'd be ok buying this one to upgrage it to an XM one? Are all XM/BX variants the same fitment?

http://www.ebay.co.uk/itm/300599987277? ... 1423.l2649

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Post by mat_fenwick » Fri Oct 14, 2011 12:11 am

I've replaced mine with an XM front centre sphere (not the XM accumulator sphere linked to) about 2 years/30k miles ago with no problems. I also changed the pump at the same time, so can't say what difference the sphere itself made.
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1993 1.9 TZD Turbo Estate
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1993 VW LT35 campervan
1985 Hyundai Stellar V8
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Post by Des Smith » Fri Oct 14, 2011 12:15 am

Rob,

Other people will be able to give you chapter and verse on the upgrade, but is your pressure regulator OK? You might want to talk to Martin at Pleiades - what he doesn't know about Citroen hydraulics will fit on a postage stamp. He will do a recon exchange regulator if you need one.
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Post by citronut » Fri Oct 14, 2011 9:15 am

one thing to add is smear the new or old sphere seal with citro blood (LHM) before re/fitting any sphere,

also on your acumalator sphere fitting instructions you did not state to move the hight lever to the high setting after shutting the bleed valve,

so no the car will not rise :roll: :lol: :wink:


citroen say after doing work on the hydraulic systen to leeve the bleed screw open with the engine ticking over for 2 minuites, then hold the revs at about 2.5K whilst closeing the bleed valve,

regards malcolm
curent ride
K reg BX 17TD TZD est
also own
K reg D special

no longer have
H reg CX saffari 2.5 TRI (now gone to Malaysia)
R reg xantia 1.9TD est (gone to meet its maker)

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Post by robt » Fri Oct 14, 2011 2:43 pm

All advice noted, cheers.

I'm getting the clicking sound from the pump every 5 seconds so I'll work my way through replacing parts one by one, trying to save spending too much unnecessarily :) I tightened up some of the unions on the regulator and elsewhere as they were a bit loose.

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Re: Changing Spheres

Post by marcdublin37 » Fri Sep 07, 2012 4:51 pm

Think I will print this off as rear spheres need doing, great guide cheers.

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Re: Changing Spheres

Post by Geoffrey Gould » Sun Sep 09, 2012 10:05 am

Hi Great write up but I find myself somewhat confused by the reference to Gas volume being 62 BAR ( and later 70 BAR.) Bar is surely Pressure, 14.7 psi or 1 atmosphere if I remember correctly, volume is capacity, as in 400 cc or 1pint,gallon whatever. Just examples not saying that 400cc is a gallon !!!!
Still confused.
G
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Re: Changing Spheres

Post by mat_fenwick » Mon Sep 10, 2012 5:20 pm

You are right, it doesn't make sense! I missed that when I added this here. It would make sense if the description of pressure is correct, so I have edited the first post.
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Re: Changing Spheres

Post by KevR » Tue Nov 20, 2012 6:02 pm

Is there any real need for repeated opening and closing of the 12mm bleed valve after sphere changes? I've just changed all five and the system sorted itself out within half a minute and lifted as normal, so I didn't bother. If I should have bothered, someone please let me know and I'll go and do it!

Edit: just seen Malcolm's post about Citroen's advice on the matter, so I'll go back and do that tomorrow.
1990 BX TZD Estate ('the grey one', 1991 BX TZD Estate ('the white one'), 1982 2CV6 Charleston (in bits), 1972 AZU Serie B (2CV van), 1974 HY72 Camper, 1990 Land Rover 110 diesel LWB, 1957 Mobylette AV76, 1992 Ducati 400SS, 1966 VW Beetle, 1990 Mazda MX-5, 1996 Peugeot 106D, 1974 JCB 2D MkII, 1997 BMW R1100RS, 1987 Suzuki GSX-R1100, 1978 Honda CX500A, 1965 Motobecane Cady, 1988 Honda Bros/Africa Twin, 1963 Massey Ferguson 825, and a lot of bicycles!

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Re: Changing Spheres

Post by Defender110 » Tue Nov 20, 2012 9:23 pm

If the system sorted itself out within a minute then I wouldn't bother Kev, any air that might have been in the system will now have passed through, it's just some cars don't even start rising until the bleed screw has been left open. The Citroen advice is just to cover all options.
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Re: Changing Spheres

Post by KevR » Wed Nov 21, 2012 9:52 am

That's good - saves a bit of hassle!
1990 BX TZD Estate ('the grey one', 1991 BX TZD Estate ('the white one'), 1982 2CV6 Charleston (in bits), 1972 AZU Serie B (2CV van), 1974 HY72 Camper, 1990 Land Rover 110 diesel LWB, 1957 Mobylette AV76, 1992 Ducati 400SS, 1966 VW Beetle, 1990 Mazda MX-5, 1996 Peugeot 106D, 1974 JCB 2D MkII, 1997 BMW R1100RS, 1987 Suzuki GSX-R1100, 1978 Honda CX500A, 1965 Motobecane Cady, 1988 Honda Bros/Africa Twin, 1963 Massey Ferguson 825, and a lot of bicycles!