Spheres, Hydraflush and Brake Bleeding

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Post by CitroJim » 08 Mar 2009, 15:29

Steve, I've just re-read your post. I assumed you meant the Anti-Sink sphere when you spoke of the rear centre sphere. I'm sure you mean the Anti-Sink but just in case, read on...

There is another rear centre sphere on VSX models and this is the rear hydractive sphere.

Changing this one is an almost guaranteed douche vert as it's very hit and miss as to whether or not it depressurises or not due to the interaction of the hydractive electrovalve and the anti-sink valve.

Hydractive spheres often have to be unscrewed under pressure and this can be a real test of your chosen sphere removal weapon. best to put a bowl under the sphere, start it on it's journey until it is leaking LHM freely and then go off for a cuppa. By the time you come back, the pressure will have dissipated.

No such worries if yours in not a VSX/Activa/Exclusive. Ignore what I've said!

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Post by demag » 08 Mar 2009, 17:07

Yes to change a rear centre hydractive you don't need to disconnect any pipework. But I found on my Xm (similar) a good pair of Stillsons to hold the bracket with will help when undoing the sphere.

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Post by StevieM » 08 Mar 2009, 21:31

Tks for your responses.
I'll have a go early a.m.
Rgds, Steve

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Post by StevieM » 08 Mar 2009, 21:32

To clarify...single sphere...presume anti-sink one!!

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Post by red_dwarfers » 08 Mar 2009, 21:40

Single central sphere + nut for undoing pipe from sphere = anti sink :wink:

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Post by StevieM » 09 Mar 2009, 17:51

All went OK.
See what you mean about 9mm nut hard to get at....much flipping of spanner/tiny arcs of movement.
When pulled the pipe (required sphere removal to aid teasing pipe out of sphere), it was all a bit of a non-event......no hissing/squirting...not so much as a drop spilt. (maybe sphere was good, having already expelled all fluid with its pressure??)
Sphere certainly was not full......placed on kitchen scales, with brand new one.....new one was even slightly heavier!!
While under car, cleaned up all the rusty union nuts I could see with spark plug brush, and painted some grease over them all with small brush.
Bled rear brakes.......will not touch now 'til have done my 1-2000 miles of
hydraflush treatment.
All info on this thread very much appreciated....-
MANY tks, Steve

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Post by CitroJim » 09 Mar 2009, 18:06

Good on you Steve :D 8)

yes, the A-S is a bit of a 'mare for access. What is needed is a ratchet open-ended 9mm spanner :lol: :lol:

I'm not sure weighing spheres is a positive methiod to determine their goodness. A sphere pressure tester is the only sure way...

Pleased all the advice in this thread was helpful :D

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Post by Davo » 15 Mar 2009, 16:58

I managed to do the whole process on my ‘98 Xantia yesterday in about 5 hours. Thanks to CitroJim and the other posters for all the advice- it made what could have been another nightmare Citroen job relatively painless. Since I wanted to do the sphere change and LHM change in one fell swoop I chose to put the front up on ramps first, crack off the accumulator sphere by 1/8 of a turn (just enough so that it could be removed from above by hand once depressurised- otherwise this would be a pain to get to with the tool). Then when I turned the car around and put the back up on ramps I could do everything else without moving it again. Notes from my experience:

• Ramps made the job much easier in my opinion. I found some decent ones on Screwfix (part no 83061) for £33, and if you can make it up to £50 then postage is free.

• Like StevieM I also used the Halfords 9x11mm flare spanner (part no 470112), it worked well to loosen the anti-sink sphere nut but once it was loose I needed another open-ended spanner with a different offset angle since the space is so tight I couldn’t get the swing with just the flare spanner.

• Not sure if the PlusGas treatment was merely a psychological boost but having sprayed every joint with it beforehand I had no problems (this was using the Pleiades tool though, highly recommended to make life easier for ‘just’ £35 + postage!)

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Post by jonathan_dyane » 15 Mar 2009, 17:12

Just a note to say that one may remove the accumulator sphere with the suspension on high without pressure loss/the car dropping, which makes for easy underneath access however I strongly recommend using axle stands just in case.

NB, I am referring to the anti-sink Xantia here; I cannot remember whether this works on non anti-sink cars.

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Post by CitroJim » 15 Mar 2009, 17:27

jonathan_dyane wrote:Just a note to say that one may remove the accumulator sphere with the suspension on high without pressure loss
I can confirm that Jonathan :lol: My V6 is currently minus not only an accumulator but the whole PR block and LHM reservoir and still it's at normal ride height at the back despite the front being on axle stands :lol: :lol:

In fact it'll cause a problem when I need to withdraw the gearbox so I'll have to support the rear and go in and crack off a rear sphere...

"Sinkers" I would have thought, will sink a bit quicker if the accumulator is cracked and system pressure falls although the height correctors will hold it for a while along with the security valve and FDV. Any movement that provokes the height correctors into action will cause a very quick fall in theory... Next time I get my hands on my "sinker" I'll try it out and see what happens.

As you say, always play safe and use stands whenever doing anything with the suspension and hydraulics...

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Anti-Sink Sphere / Brakes

Post by SLYTZD » 26 Mar 2009, 21:05

Just changed my Anti Sink Sphere on my Activa. Thanks for the tip about the 9mm flare spanner from Halfords, £5 well spent, good fitting spanner & lifetime guarantee. I have been planning to change all the rear spheres for a while so have been soaking them in WD40 for a while. As a result I managed to do the whole job with ease in less than an hour & interestingly only literally 2 or 3 drops of fluid loss.

The reason for changing it was a seemingly not uncommon problem that the brakes seem to be either on or off with not much in between. Already FULLY bled the system, cleaned the LHM filters & currently have Hyroflush in, replaced the Accumulator sphere, front flexible brake pipes, with no improvement. Will take it for a road test tomorrow to see if replacing the AS sphere has helped.

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Re: Spheres, Hydraflush and Brake Bleeding

Post by xantia 1.9td 1999 » 29 Mar 2009, 11:05

CitroJim wrote:A question that is often asked is how to replace spheres, how to change the LHM, use Hydraflush and bleed brakes. This is a (hopefully) a concise guide to these three related jobs. I post here so that comments may be added and "peer reviewed" before it is moved to a more appropriate area of the forum.

Pre Requisites

Before starting, ensure you have the following tools and sundries:

A good sphere removal tool. Either the genuine Pleiades item or a "Xac Special" A tool is essential

Ramps and axle stands

A 12mm spanner for the bleed valve on the pressure regulator, a very good, slim 8mm ring spanner for the caliper bleed nipples and a very high quality 9mm flare nut spanner for the union on the anti sink sphere.

A clean 500ml glass jar and a length of plastic hose that is a snug fit on the bleed nipples.

A jar of clean petrol and a clean paint brush

A 4.5mm hydraulic seal for the Anti-Sink Sphere

A normal household broom (you'll see why later!)


Starting with the most difficult, the rear corner spheres. These are often very tight and their removal MUST be carried out initially with the suspension on high and under full pressure to avoid damage to the suspension cylinders. The car MUST be very firmly supported and preferably on ramps. In any case, so supported that if it suddenly drops it won't crush you. So, up on ramps, engine running and suspension on high, you need to apply the sphere tool and "crack" each sphere off by about an eight to a quarter of a turn (i.e. just get them started). They will be tight and you may need to use your boot to get them moving. Once they are moving, put the suspension on low, depressurise by opening the 12mm bleed valve on the pressure regulator by no more than half a turn and go back, still ensuring the car is fully and safely supported and unscrew them fully. Be prepared for LHM spillage. Clean up, recover the old sphere seals if they got left behind in the groove on the sphere housing. Get your new sphere seals, dip them in clean LHM and place them in the groove, never place them on the sphere as they will not seat properly and may get cut. Screw the new sphere on hand-tight only.

Whilst you are there, do the Anti-Sink sphere. This is the one in the middle rear. before you can unscrew it, the small hydraulic pipe going into the rear of it MUST be undone and pulled out. For this you need the 9mm Flare Nut spanner. The union may be tight and take care not to round it off, hence the good spanner. A bit of Plus Gas is a good idea to help it along. Once the union nut is undone, pull the hydraulic pipe out of the sphere and note if the hydraulic seal came out with it. More than likely it will have stayed in the sphere. You MUST use a new one on installing the new sphere. Again, be prepared for a good spill of LHM.

You can now undo the old sphere off the bracket. It may be tight and the bracket is not that strong so take care. Strictly, this sphere does not need a new ring seal but it's not a bad idea to fit one. Screw the new sphere into the bracket, dip the new pipe hydraulic seal in LHM and fit it over the end of the pipe until it rests against the flare on the pipe. Push the pipe into the sphere and screw up the union. They don't need to be done mega tightly and it'll be about right when it is as far into the new sphere as it was in the old, usually thios depth can be gauged by where the rust begins on the union threads. On repressurising the system, check for leaks and if there is a weep, just nip the union up a touch until the leak stops.

They're the hard ones done. The front corners are easy, Just undo them (with the system on low and depressurised of course) be prepared for spillage, clean up, dip the new seals in LHM, place the seals in the grooves and screw the new sphers in hand-tight.

The same applies to the accumulator but access is often poor and you really need the front end up on ramps or stands to get good access to it to enable a good swing on the removal tool. The Accumulator is often very tight. Mind the radiator! Again, clean up, Dip the seal in LHM and place in the groove before screwing the sphere in hand-tight.

Finally, nip up the 12mm bleed valve, start up, allow pressure to come up, set on high, top up the LHM and do a really good session of Citarobics.

LHM Change

Set on low, depressurise, disconnect all the rubber pipes on top of the LHM reservoir. If the original clips are in place, carefully prise them apart with a scriber or small screwdriver before pulling the pipes off. They can be reused with care and need a small pair of pliers to clip them up again.

Undo the two 10mm nuts holding the reservoir and lift it out full of the old LHM. This is the easiest way. Release the spring clip across the top, lift out the filter head and place it in a clean receptacle to drain. I use the bottom of a 4 pint milk carton.

Pour the old LHM into a suitabel container ready for disposal at your local tip. Use the waste engine oil facility.

Clean out the LHM reservoir with clean, lint-free rag (blue paper is ideal) and them remove the two filters from the filter head and clean them in petrol. One is clipped on and is secured with a small "S" shaped wire clip and the other is secured with a bayonet fitting and is long and conical. It is easily missed as it lives up inside the suction tube. Wash them with a paint brush in petrol until they are spotless and leave to dry. The filter mesh is delicate so don't be rough with them.

Reassemble the LHM reservoir and refit to the car. The clips that hold the pipes on to the reservoir can be reused with care or "Jubilee" clips can be used instead.

Refill the reservoir with either LHM or Hydraflush. It'll take at least 4 litres.

Close the pressure regulator bleed valve, start up and set the suspension on high, top up the reservoir and do thorough citarobics. Recheck the level.

Bleeding Brakes

With the front wheels off and up on stands, locate the front caliper bleed nipples. Pop off their protective rubber caps, clean up around them, spray them with Plus Gas and carefully crack then open with your 8mm ring spanner. Nip them up again. leave the spanner on and place the plastic pipe on the nipple and lead it into a jamjar. Start up and apply the brakes by jamming the end broom between the seat and brake pedal (now you see what the broom is for!). Open the bleed nipple and watch LHM run ito the jamjar. When free of air and all the old, dirty fluid is flushed through, nip up the nipple, slip off the pipe, replace the rubber cap and repeat on the other side. Top up the LHM reservoir with the equivilent amount you bled out.

The rear brakes MUST be bled with the suspension set on high and with weight on the back wheels. On cars with alloy wheels it is sometimes possible (depending on the wheels) to get at the nipples without removing the wheels but on most, the wheels have to come off and that makes a problem of how to keep a load on the back wheels. Best is to do one wheel at a time and keep the other on the ground and thus loaded.

Do the same as for the front but do bleed at least 250mL of fluid out of each nipple as the rear brake lines are very long. Keep an eye on the LHM level and top up as necessary. You will know the level is low as the STOP light will come on. Don't let the level drop too low.

Job done. If you have used Hydraflush, leave it in for al least 1500 miles and them change for proper LHM it by repeating all the above procedure, including cleaning the filters again.

Recheck levels and do citarobics again.

Job's a good 'un

Please add to this as I'm sure to have forgotten something!

[Edited to correct the A/S sphere union nut size and hydraulic seal size :oops: ]


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Post by coolderry » 12 Apr 2009, 13:30

Great forum, i have been lurking for a while getting loads of top tips and info!!!

However i have a sphere related problem on my 1995 1.8i 16v Xantia.
Had the car for about 5 years now and had no problems.

Just went through its MOT and it failed on back brakes, lack of braking force. Instant thought... change the rear spheres.
Took them off, and they were needing replaced.


I have never had problems getting the correct spheres before. Took 'em off, walked into local factors 'i'll have 2 of these please', bish bash bosh job done.

But now im having problems getting ones like the ones that came off!!!

I have tried to get the GSF download for spheres, but it doesnt seem to work.

The factors have been trying to give me smaller ones than the ones that came off, and its the 3rd attempt now.

Is there a foolproof way to identify the ones i have? Would i be able to use the smaller ones the factor is giving me?
The new ones are smaller, but the thread length also seems shorter.



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Post by CitroJim » 12 Apr 2009, 14:05

Hi Simon,

I can dig out the original spec. for your spheres no problem at all. I have it here somewhere :roll:

The GSF ones should be OK. They're normally after-market AMTEX ones and generally they're perfect and highly rated quality-wise. Can you advise the GSF part. Number of the ones you have been offered and then a confirmation can be made.

The correct GSF one should be N45366. Provided they're green and round they should be Ok despite the shorter thread. I've seen that myself but it never seems to cause a problem in-service. I'm not being sarcastic in asking if they were round and green as you may have been offered substitute grey mushroom-shaped spheres used on the C5. These can be used but a thread adaptor is needed. They indeed do have smaller and shorter threads.

I doubt this is the full cause of your rear brake issues. It's more likely a build-up of corrosion on the calipers leading to reduced efficiency. The main area of corrosion that causes most problems occurs between the caliper and its mating face on the trailing arm. The corrosion pushes the caliper out of line with the disc and a dead give-away is the pads will have worn wedge-shaped. There is loads of posts on here about it and a search should find a few.

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Post by coolderry » 12 Apr 2009, 18:56

Thanks for that CitroJim.

The spheres i have been given, are AMK automotive components, the part number is S 10N. The previous spheres which i have replaced (front ones), and which i still have the box for are AMK S 09N's.

The factors advise me that they are the ones for the job, and they are for the 93-95 model. The 95 onwards spheres are (apparently) the same size.
I believe that the part number for the later rear ones are S 100N.

I'll get these spheres done and then give the rear brakes a good going over. I got front and rear discs, and front and rear brake pads still to fit courtesy of eBay when the time comes for it to need them......

Have you had any experience of the AMK spheres?