Spheres regased but...

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Spheres regased but...

Post by xantos »

It's me again...

Yesterday I got my spheres re-gassed by a Citroen specialist, who is now retired and has worked for Citroen service. He is 83 years old, but still has a strong hand and a clear head! Has a homemade sphere tester and re-gasser.

The main accumulator sphere was ruptured and both front and back corner spheres were at 60%. Tested the rear center and balancing spheres, they were ok, but couldn't unscrew the anti-sink sphere. But he said that the anti-sink doesn't fail, and also the center and balancing spheres doesn't fail, so we didn't bother of taking the front spheres off (center and balancing).

Did a session off citaerobics (3 times up and down) and I drove home. The ride has improved only a little and I was really disappointed. When I got home and did citaerobics again and noticed that there were bubbles in the LHM tank when car on low. Left the car on low and engine running for 15minutes and almost all the bubbles have disappeared. When I released the pressure on the pressure regulator there was an avalanche of bubbles to the LHM tank. Left it again for 15minutes till all the bubbles were gone and went for a ride. And it was FANTASTIC! Made a few kilometers and then parked the car. Went for a ride 1 hour latter and it was not near as good as it was...

So where are the bubbles coming from?

The work I have done so far:
- resealed the pressure pump
- changed the suction pipe (pump - LHM tank)
- changed 2/3 of the octopus
- resealed the brake dosser valve
- diode mod
- "10minutes mod"
- LED diode mod (for observing electrovalves during drive)

I experienced a really smooth and soft drive and now I am determined to get to the bottom of this!

Any thoughts would be appreciated...
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Re: Spheres regased but...

Post by isisalar »

I did battle with the bubbles this year by doing most of the things you've done and changing ALL the spheres and the ride is now very good, given the things you've done I would suggest that the most likely candidate for the bubbles is nitrogen, if there's any left, coming from these 3 supposedly everlasting remaining spheres. They're not everlasting and the 'center and balancing spheres' front and rear are largely responsible for the soft ride, I'd get them changed if I were you. The anti sink is also important so start giving it some plus gas.
Coincidentally I decided to check my LHM level yesterday and do a citrobics session and also found bubbles in the tank on low which didn't surprise me as it seems virtually impossible to eradicate and doesn't seem to affect the ride that much if at all but it did prompt me to check all the jubilee clip connections on the tank to pump feed hose I'd made up in the summer, I'd tightened them all as much as possible back then but they all now needed a further tighten up, perhaps they've stretched or it's the cold weather so something to check.
The good news is that having done a very similar citrobics bubble clearing process to yourself the ride was no better than normal so looks like things are fine with mine.
I'd love to hear why these bubbles appear on low/de pressurised if anyone can explain it.
If you run your car on high for about 1/2 hour it will be just about as bubble free as possible, check out the ride then to see how it should be, if it deteriorates markedly there's bubbles getting in.
Best of luck with it.
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Paul
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Re: Spheres regased but...

Post by Northern_Mike »

xantos wrote:.... but couldn't unscrew the anti-sink sphere. But he said that the anti-sink doesn't fail, and also the center and balancing spheres doesn't fail.

Any thoughts would be appreciated...
My thoughts are that he couldn't be bothered to fight with the stuck spheres and lied to you. They can and do fail. They'd all failed in my Activa and at least 2 other Xantias I've been involved with.

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Re: Spheres regased but...

Post by Peter.N. »

If its hydractive the centre spheres are mainly responsible for the soft ride, if they are flat it will be hard.

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Re: Spheres regased but...

Post by Mandrake »

xantos wrote: The main accumulator sphere was ruptured and both front and back corner spheres were at 60%. Tested the rear center and balancing spheres, they were ok, but couldn't unscrew the anti-sink sphere. But he said that the anti-sink doesn't fail, and also the center and balancing spheres doesn't fail, so we didn't bother of taking the front spheres off (center and balancing).
I agree with Northern Mike's comment - its completely untrue that the anti-sink and centre/balancing spheres don't fail. In fact its more likely to find a failed/ruptured anti-sink sphere than the others in my experience - as there is no obvious symptom from a failed anti-sink sphere they get overlooked and never or seldom replaced. All the Xantia's I've had dealings with (two of my own, one belonging to my Dad) had completely ruptured anti-sink spheres when we bought them, with no obvious symptom until the sphere was removed and oil squirted out in a fine jet. (A sure sign of a ruptured sphere)

I also agree with Peter N's comment that a large part of the soft ride comes from they hydractive centre spheres - and they too get overlooked for replacement because those used to the old hydropneumatic system (including a lot of garages) replace the corner strut spheres when the ride becomes harsh but fail to appreciate the importance of the hydractive centre spheres, or even be aware of their existence or function. The rear hydractive centre on my previous Xantia was old and punctured when I bought it even though the rear strut spheres had been replaced by someone less than two years prior, so don't assume that your front hydractive centre will be ok - unless its a 3 dimple multilayer diaphragm type it wears out just like the rest and at a similar rate.
Did a session off citaerobics (3 times up and down) and I drove home. The ride has improved only a little and I was really disappointed. When I got home and did citaerobics again and noticed that there were bubbles in the LHM tank when car on low. Left the car on low and engine running for 15minutes and almost all the bubbles have disappeared. When I released the pressure on the pressure regulator there was an avalanche of bubbles to the LHM tank. Left it again for 15minutes till all the bubbles were gone and went for a ride. And it was FANTASTIC! Made a few kilometers and then parked the car. Went for a ride 1 hour latter and it was not near as good as it was...

So where are the bubbles coming from?

The work I have done so far:
- resealed the pressure pump
- changed the suction pipe (pump - LHM tank)
- changed 2/3 of the octopus
- resealed the brake dosser valve
- diode mod
- "10minutes mod"
- LED diode mod (for observing electrovalves during drive)

I experienced a really smooth and soft drive and now I am determined to get to the bottom of this!
Ahh, now you've been bitten by the bug. :-D Once you've experienced the system working as it should even for a short time, its very hard to go back to a harsh ride... :( I feel your pain as I know how frustrating this can be...

ANY source of air or nitrogen bubbles accumulating in the hydraulic system can and will cause ride harshness, and as you observe there are many potential sources - only when ALL of the possible causes are eliminated will the ride be smooth and crash free, and stay that way without frequent citrerobics. (which is only ever a temporary cure if there is a significant source of air/nitrogen ingress)

You've missed two possible causes of air/nitrogen ingress.

I think Paul is right on the money with his suggestion of nitrogen bubbling out of failing spheres - we know that you haven't replaced or tested your anti-sink sphere - which is connected to your rear suspension, and that you haven't tested or replaced your front hydractive sphere - which is obviously connected to the front suspension.

When spheres reach the end of their life they start leaking nitrogen at an accelerated rate, when the diaphragm ruptures the leakage rate of nitrogen goes up orders of magnitude. This is a big problem with anti-sink spheres since they rupture without obvious symptoms.

My Dad's Xantia came with a ruptured anti-sink sphere and it was bubbling so much nitrogen into the system that the rear brakes were needing to be bled every two weeks otherwise they'd more or less stop working. (The rear of the car was lifting and hitting the upper limit stops during braking through lack of rear braking effort)

I bled them every couple of weeks three times in a row but the nitrogen kept coming and kept filling the rear brake lines within a couple of weeks of use. It wasn't just a small amount of air, it was masses of air and froth, as if most of the brake pipe length from front to back was full of air. After I replaced the anti-sink sphere (which squirted oil after being removed proving it was ruptured) and bled the brakes one more time the brakes never needed to be bled again.

Granted the brake lines are a dead end so tend to collect air more easily, but with such a high nitrogen leakage rate and the anti-sink system preventing self bleeding over night air could easily accumulate in the rear suspension. If your front hydractive sphere is near the end of its life it may be bubbling significant quantities of nitrogen into the front suspension too.

I did the "10 minute mod" on my car about 5 months ago and for nearly 3 months the ride was absolutely smooth and crash free then a couple of months ago I started to notice the ride deteriorating, then a couple of weeks ago the deterioration has accelerated.

The front strut spheres are definitely very low on gas making the front nearly rigid in the hard mode and will need replacing soon, but I also noticed recently that the "harshness" is back again, especially at the front. Doing thorough Citrerobics does make quite an improvement for a short while - the ride remains stiff but looses its "harshness/crashiness", then it creeps back in within a day or so.

I did have a minor leak on the hose going into the hydraulic pump recently but thought I fixed it, so I couldn't understand where air might be getting in from. Then today it suddenly dawned on me - that with rapid pressure loss in the front spheres that nitrogen must be going somewhere... #-o

I realised that the source of "air" that has caused the ride to become quite harsh again is the nitrogen bubbling out of the spheres during their "last gasp" of life...citrerobics temporarily flushes that nitrogen out but it quickly builds up again.

So definitely get the remaining spheres replaced before you spend too much time looking into other possibilities. I'd almost guarantee that your anti-sink sphere will be ruptured.

The other possible source of air ingress which you haven't listed above is in the power steering return line. The flow through the power steering is 3x the volume of the flow through the pressure regulator that feeds the suspension and brakes, and the flow is maximum when the steering is at rest. If you have a weep on your power steering low pressure return hose it could potentially be sucking air there.

Likewise a slight leak on the large diameter low pressure return hose from the pressure regulator to the tank (via the octopus ?) is a possibility.

One final comment on re-gassing spheres versus replacement - its generally accepted that spheres shouldn't be left to go below about 50% of their normal pressure before re-gassing them, otherwise permanent damage/fatigue to the diaphragm can occur. While re-gassing is often successful, if you don't know the history of the spheres its not always a good idea.

Accumulator spheres in particular don't re-gas as well as the others, possibly because they're subject to the highest pressure of any spheres on the car, all the time. Over the years I've had two accumulator spheres that we re-gassed ourselves fail within minutes of being fitted to the car and pressurised - they literally went "splat", with both the diaphragm and seal at the filler cap failing at the same time. If your accumulator sphere was also re-gassed and not replaced, it could be that it's bubbling nitrogen - which could explain the large quantity of bubbles you saw when you opened the bleed screw.

With the bleed screw closed the return flow from the regulator to the tank bypasses the sphere, but when you open the bleed screw the oil from within the sphere is expelled and returns to the tank.

It could be that one or more of your spheres have developed high nitrogen leakage rates through age, if this is the case re-gassing them will not cure the leakage rate problem - so potentially some of your re-gassed spheres whilst at their correct pressure (for now) could still be a cause of nitrogen bubbling into the suspension at an excessive rate. Only new replacements would eliminate that possibility.
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Re: Spheres regased but...

Post by Xaccers »

Just because of my OCD;

If you remove a sphere and LHM sprays out, the sphere is not ruptured, it's just very very flat. So flat that it doesn't have enough pressure to expel the LHM when you depressurise the system.
If it just dribbles out when you hold the sphere with the hole to the ground, then it has ruptured.
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Re: Spheres regased but...

Post by Mandrake »

Xac wrote:Just because of my OCD;

If you remove a sphere and LHM sprays out, the sphere is not ruptured, it's just very very flat. So flat that it doesn't have enough pressure to expel the LHM when you depressurise the system.
If it just dribbles out when you hold the sphere with the hole to the ground, then it has ruptured.
Not sure that I can agree with that Xac.

If the diaphragm is not ruptured there will always be some pressure behind the diaphragm to push it down as pressure loss through the membrane is asymptotic to zero, and it takes almost no pressure to push the soft diaphragm down to the bottom before the sphere is removed from the car.

Think about it - even 2 psi of pressure remaining (when there should be between 440 and 1100 psi depending on sphere) would be greater than the weight of a 2 lb lump hammer pushing down on the centre of the diaphragm as the surface area would be several square inches. It's not like it would take several seconds for the remaining oil to be pushed out after the sphere is removed from the car - the diaphragm will already be bottomed inside the sphere well before you unscrew the sphere off the car.

A ruptured diaphragm is often only a tiny hairline crack in the membrane, during operation oil will find its way through the crack into the gas pocket behind the diaphragm so you'll have a mixture of oil and remaining gas. When you de-pressurise the car and remove the sphere you now have a mixture of oil and pressurised gas with a tiny crack so the oil is forced out over a long period of time, hence a small fountain of oil.

I've seen the fountain of oil last for over a minute - especially on anti-sink spheres. It's the tiny size of the rupture that allows it to carry on for so long. I would also point to the example of the anti-sink sphere I gave above, that was releasing so much nitrogen that I was bleeding the brakes every two weeks. That particular sphere produced a minute long fountain when it was removed, not just a quick squirt. It still had quite a bit of pressure in it, it was just that the diaphragm was cracked...there is no way that amount of nitrogen was passing through an un-compromised diaphragm.
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Re: Spheres regased but...

Post by Xaccers »

Mandrake wrote:
Xac wrote:Just because of my OCD;

If you remove a sphere and LHM sprays out, the sphere is not ruptured, it's just very very flat. So flat that it doesn't have enough pressure to expel the LHM when you depressurise the system.
If it just dribbles out when you hold the sphere with the hole to the ground, then it has ruptured.
Not sure that I can agree with that Xac.

If the diaphragm is not ruptured there will always be some pressure behind the diaphragm to push it down as pressure loss through the membrane is asymptotic to zero, and it takes almost no pressure to push the soft diaphragm down to the bottom before the sphere is removed from the car.

Think about it - even 2 psi of pressure remaining (when there should be between 440 and 1100 psi depending on sphere) would be greater than the weight of a 2 lb lump hammer pushing down on the centre of the diaphragm as the surface area would be several square inches. It's not like it would take several seconds for the remaining oil to be pushed out after the sphere is removed from the car - the diaphragm will already be bottomed inside the sphere well before you unscrew the sphere off the car.

A ruptured diaphragm is often only a tiny hairline crack in the membrane, during operation oil will find its way through the crack into the gas pocket behind the diaphragm so you'll have a mixture of oil and remaining gas. When you de-pressurise the car and remove the sphere you now have a mixture of oil and pressurised gas with a tiny crack so the oil is forced out over a long period of time, hence a small fountain of oil.

I've seen the fountain of oil last for over a minute - especially on anti-sink spheres. It's the tiny size of the rupture that allows it to carry on for so long. I would also point to the example of the anti-sink sphere I gave above, that was releasing so much nitrogen that I was bleeding the brakes every two weeks. That particular sphere produced a minute long fountain when it was removed, not just a quick squirt. It still had quite a bit of pressure in it, it was just that the diaphragm was cracked...there is no way that amount of nitrogen was passing through an un-compromised diaphragm.
The logic behind my theory is nitrogen isn't as dense as LHM, so if you held the sphere upright (the hole to the sky), the nitrogen would escape first so wouldn't push any LHM out and you'd have a sphere with just LHM in it which would then dribble out, yet with spraying spheres they spray even when held upright. I'm sure Jim and I have tested one that did this and it held pressure so it hadn't lost all the nitrogen suggesting that the membrane wasn't ruptured.
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Re: Spheres regased but...

Post by Mandrake »

I see your line of reasoning, but why would you assume that the rupture must be at the bottom of the sphere - eg right at the top when the sphere is held upside down ? :)

What if the rupture is half way up the side of the diaphragm where it flexes the most, (as I believe is probably the case) in which case the hole is not at the top of the sphere when held upside down, but closer to half way down the side.

A ruptured sphere is usually about 90% full of oil behind the diaphragm so in an upside down sphere I could easily see a small pocket of gas at the top (neck end) which is above the hole so it would be oil at the location of the hole with the gas pressure forcing it through the hole and into the space between the diaphragm and the wall - which is not designed to be air tight, so would leak down between the diaphragm and inner wall and through the neck.

That's my theory anyway.
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Re: Spheres regased but...

Post by Xaccers »

Mandrake wrote:I see your line of reasoning, but why would you assume that the rupture must be at the bottom of the sphere - eg right at the top when the sphere is held upside down ? :)

What if the rupture is half way up the side of the diaphragm where it flexes the most, (as I believe is probably the case) in which case the hole is not at the top of the sphere when held upside down.

A ruptured sphere is usually about 90% full of oil behind the diaphragm so in an upside down sphere I could easily see a small pocket of gas at the top (neck end) which is above the hole so it would be oil at the location of the hole with the gas pressure forcing it through the hole and into the space between the diaphragm and the wall - which is not designed to be air tight, so would leak down between the diaphragm and inner wall and through the neck.

That's my theory anyway.
The sphere is rotated several times when unscrewing it, and when it's partially unscrewed it isn't sealed so the nitrogen should match up with any split and escape first.
Either way, the sphere's shagged and needs replacing :)
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Re: Spheres regased but...

Post by Chris570 »

Xac, it's a Citroen, forget logic ;)

on the XM estate I did the spheres on I had 3 LHM jets ;)
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Re: Spheres regased but...

Post by Xaccers »

Chris570 wrote:Xac, it's a Citroen, forget logic ;)

on the XM estate I did the spheres on I had 3 LHM jets ;)
We need to test such spraying spheres for any residual pressure. If they do then the membrane is intact and my theory is correct, if no pressure remains then Mandrake's theory is correct :)
I think we should invite Kari from Mythbusters over to perform the experiment

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Re: Spheres regased but...

Post by myglaren »

Xac wrote: I think we should invite Kari from Mythbusters over to perform the experiment

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Re: Spheres regased but...

Post by Northern_Mike »

I'd happily let her.

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Re: Spheres regased but...

Post by Northern_Mike »

One of the Activas I did the fronts on were, I presume, ruptured as both just spewed out LHM as soon as they were loosened a few turns. No massive pressure, but plenty enough to make a mess.

On my own Activa both balance spheres completely covered me when they were undone.

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