Xantia Accumulator Sphere

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Has anyone got any tips on unscrewing these? I've just been trying to remove it and so far I've tried a Boa strap wrench with a rubber strap - too big
and too stretchy, a chain wrench purchased from Machine Mart http://www.machinemart.co.uk/product.asp?p 0210243&r 76&g1 - snapped when two spanners were applied and one of those strapwrenches with a socket adaptor http://www.machinemart.co.uk/product.asp?p 0210245&r 76&g1 Which still won't shift it even with one foot braced firmly against the underside of the car. The system is depressurised by unscrewing the nut on the regulator.
--
Malc

Permitted to use the outs de lan
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There is a back issue of Car Mechanic mag which covers this work, give them a look.
PDH
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Malc wrote:

from memory (wait a day or two before taking my advice)
if anyone knows better pipe up !
pressurise the system, crack the sphere but only just crack it.
depressurise the system and unscrew the sphere.
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And there are apparently 7 of the things scattered around the car.
PDH
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Paul Hubbard wrote:

7 accumulator spheres ? you sure ?
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over. If you are within reach of Chorlton cum Hardy, 'Westroen' (father and son in a suburban semi) at 7, Nell Lane will replace all the spheres with recon units at £25 each. Three year guarantee. For another £40 they drain and replace the hydraulic fluid and change the filters in the reservoir. All that while you wait in about an hour. It's all they do and they know the job inside out. Their sphere removal tool is a big steel split ring with a big tensioning bolt, welded to a heavy steel bar that gets belted with a lump hammer. You're wasting your time with filter type wrenches (and can damage the mounting block and pipes if you try- particularly the rears which get clogged with road muck and corrosion). DaveK.
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DaveK wrote:

7 accumulator spheres out of 10 ?

recon spheres ? hiow does that work then ?
"regassed" or new membranes ?
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No No No
Please don't try to even crack open the main accumulator sphere with the pressure on, you only need to do this with the rear suspension spheres and this is to stop the cylinders from moving.
To remove. Undo the 12mm bleed screw on the regulator by 2 turns max. Using a wrench, undo the sphere. Remove the O ring from the grove. Replacing, Fit the new O ring in the grove, Screw on the replacement sphere, as tight as you can get it by hand only. Start the engine and run for approx 2 mins Tighten the bleed screw.
The best tool for the job is a band wrench from Pleiades www.pleiades.uk.com Or give them a ring on 01487 831239 I have used and abused mine for years and still aint broke it.
Recon spheres ? How does that work then ? I have allways used recon spheres without any worries again from pleiades, the spheres are guaranteed for 2 years unlimited milage!! They dont have new membranes as they are sealed and I dont think that you could replace the membranes, but Pleiades tell me that the spheres are all inspected before re pressurising, thats why they can give them a long guarantee
Sorry if this post comes out twice, but I had an error message with the first time I replyed!!! Regards. Slim.
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Slim wrote:

fairysnuff ! I bow to your superior knowledge, slim ! < bows > :-)

:confused:
I've been told that the spheres which are re-gassed don't take into consideration the deterioration of the membrane. I know that the spheres are filled with nitrogen, right ? nitrogen molecules are supposed to be too big to escape through rubber (see also tyres) so why do the spheres fail ? is it the deterioration of the membrane ? where does the nitrogen go if it's not through the membranes ? if the nitrogen does escape through the membranes can it get into the LHM fluid and cause that to deteriorate ?
when I bought my xantia I noticed that 4 spheres were still under warranty and I managed to get them replaced at the main dealer when I took it in for it's 78,000 mile service. you should have seen the look on their faces when they told me that all 4 spheres needed replacing and I produced the warranty !! that's the only reason I took it into the main dealer, btw ;-)
for this reason, I haven't had the need to buy any spheres yet so I'm all ears as to why they fail in the first place. so many questions !
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This is what I like to hear, somebody socking it to a dealer....! :o)
There is a god after all.
PDH
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The gradual deteriation of a sphere is down to molecular diffusion (Grahams Law)
This diffusion takes place place as the nitrogen gas migrates through the molecular structure of the rubber diaphraghm. Much the same as a helium balloon going down, not because it's got a hole in it, just because they do!!
When you buy a helium balloon for the kids, you expect it to float up rapid, the next day or two we expect it to be on the floor, but still with no holes in it. If you had purchased a foil type balloon, this would stay up for much longer, the reason being that the molecular structure of foil is closer than rubber.
All spheres go down, we cannot avoid it, it's the way things are.
Typically on the Citroen the spheres reach about half the pressure within 3 years, if you have them recharged at this point there will be no damage to the diaphragm and they will last for another 3 years or so.
If you leave it untill the suspension is solid, the diaphragm will hit the top and at this point irreversable damage occurs, therefore your sphere is scrap metal.
The shelf life of a sphere is years and years, as when not being used the gas has to migrate not only through the rubber diaphragm, but also through the steel wall of the sphere, this takes a lot longer as the molocular structure of steel is a lot better.
When the diffusion takes place (ongoing from day one) the gas does go into the LHM system, but this is so gradual it will work it's way out to the reservoir and you wont even notice it.
I am suprised however that you managed to get a warranty claim to stick!! Most warranty companys will only pay out on sudden failure, not normal wear and tear. Lucky you !!!
Sorry its a bit long winded, but I am not to good at explaining technical bits.
Regards. Slim
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Gas diffusion through steel, eh?
Giggle.
(No, it won't happen. Which if you're a diver is probably a good thing :-) )
cheers, clive
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Gasses do indeed diffuse through metals. The rate depends on the metal, the thickness, porosity, temperature, gas, but is generally orders of magnitude below that through plastics or rubbers. And it's not inherent that the spheres have to go down. It could use a metal bellows inside, for example.
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The reason hydrolastic used to go down (apart from losing fluid) was mostly 'cos the nylon threads that reinforced the rubber crept under load. They were replaced with terylene which didn't. I know this 'cos it was one of the first reserach things my brother did for Dunlop when he joined them after leaving uni many moons ago.
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Skipweasel
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Go on, how many orders of magnitude for nitrogen through accumulator-thickness steel at room temperature? Will any make it out before the end of the solar system? (assuming it doesn't rust :-) )
cheers, clive
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Slim wrote:

I've usually inhaled it all by then :o)

ta for that. I'm having the LHM flushed & replaced & return filters blasted tomorrow for £25+ vat . if I do have to replace the spheres at any point in the future I'll bear in mind what you have said.
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Clive, Actually gas diffusion does happen through steel as steel is a molecular structure, The time taken to notice any loss at all would be years though, (luck for the divers indeed)
Regards Slim
http://www.chem.tamu.edu/class/majors/tutorialnotefiles/graham.htm
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Hydraulic system flushed, filters washed, LHM replaced. £25 ?????
If it sounds to good to be true, It normally is too good to be true!!
To flush the system First drain the fluid, remove the reservoir and wash, including filters (using parrafin) Fill with Hydraflush, then excercise the system for at least 20 mins. up, down, steering etc. Remove the wheels and bleed through each brake caliper. Drain the fluid again,. Remove the reservoir, wash again and wash the filters. Re-fill with QUALITY, ie Castrol or Total LHM Bleed through each caliper untill clean LHM is seen at each bleed nipple.
All this will take about 2-- 2.5 hours + £15 ish for the flushing fluid and £25 for LHM.
Sorry to piss on yer fireworks but thats just my opinion.
Regards. Slim.
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Slim -
Why have you given me a link to a page explaining how gas diffusion is the rate two gases mix?
How fast do you think nitrogen diffuses through steel? You earlier implied it would be sufficiently fast to explain spheres going flat. This is of course at normal temperatures, ie say 40C max. Do you think any would have escaped the spheres by the time the earth stops existing?
(What is a molecular structure in this context?)
cheers, clive
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Sorry But I already said that I am not to good at explaining tech bits!!
Gas migating through steel does happen albeit very very slowly, infact the rate is insuggnificant.
The sphere going down is gas migrating through rubber, as in a sphere the diaphragm sits about halfway up the sphere during normal use.
The rate of a sphere loosing its pressure is determined by use and heat, the front spheres and accumulator will loose pressure at the rate of about 10 bar per year, and the rears by about 5 bar per year. (under bonnet heat accounting for the greater loss)
The way I read it molecular structure is the fact that everything is made from tiny molecules!!!!!!!!!
Yeah ok sorry again wrong link??? But if you google Graham's Law you can find out all sorts of very booring info if you feel realy bored.
Regards. Slim.
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