Xantia suspension hard despite new spheres

[Jogador]

I did the bounce test, there's plenty of movement in the suspension, very bouncy...

That's what's annoying me, all the components seem fine, the lhm is fresh but still, the car doesn't behave as it should.

I did get a line on a good deal for new original spheres, as a last resort.

[cc101]

Could be worn struts or an air leak somewhere, pull down the gaitors on the front struts and apply some LHM to the cylinders. Is the LHM frothy in the tank, if so air is getting in somewhere.

Chris.

[Mandrake]

If the ride feels bouncy and harsh it could indeed be an air leak causing air bubbles to be drawn into the hydraulic pump and hence the suspension...

One way to check that is to lift the car to the maximum height setting, let the engine idle for about 3 minutes to let the suspension reach full pressure then shut the engine off and leave the car right up for maybe 15 minutes or more during which time any air bubbles will tend to coalese at high points in the suspension piping.

Then start the engine again, lower the height back to normal ride height (NOT right down like a full citrorobics session) then go for a test drive... If the ride is dramatically smoother and more stable feeling (not bouncy or harsh) then its almost certainly air getting into the suspension, as lowering the suspension back down again will temporarily flush out any air bubbles from the suspension.

In that case the first thing to check for air leaks would be to each end of the hose from the hydraulic tank to the high pressure pump. Remember the hose is under suction when running and oil is much thicker than air thus a small leak will let air in but not oil out. The next thing to check would be the o-ring on the small blanking plug at the top of the hydraulic tank indicated in red in the following picture:

http://homepages.igrin.co.nz/simon/imag ... t-plug.jpg" onclick="window.open(this.href);return false;

A leak at this seal would allow air to be sucked into the pump...(why that plug and o-ring exists at all baffles me as it seems to serve no purpose other than to be a point of failure... and I'm not sure that all Xantia's have one. Anyone know what it's purpose is ?)

[Jogador]

The air leak idea sound plausible, I was fiddling with the intake pipe on the hydraulic pump because the joint was slightly green, maybe I didn't tighten the union enough (but I did stop the leak), or maybe I damaged it... It has been known to happen to me
Will first try the test with raising the car.

As for the struts, just got new tyres delivered and will mount them later this week, this will be a perfect opportunity for lubricating the struts. Even if this is not the cause, it certainly won't hurt them

I may even snap a few pictures, just to show off

A silver Mk2 to me looks great (inferior only to v6 activa in red, in my book), and I'm especially proud to have dug up a set of original V6 activa alloy wheels (no center hole; I scoured the country to find them, it's a good thing it's such a small country), and just had them refurbished

[Xantidote]

I was fiddling with the intake pipe on the hydraulic pump because the joint was slightly green

As a temporary measure, to see if the intake pipe joint is the problem, and allowing air into the hydraulics, you could give it a good coating of grease, to stop air ingress. This was a suggestion many years ago to check for defective fuel supply line joints on BX diesels, as they could draw air in through the faulty joint, allowing the fuel to run back to the tank, causing difficult starting. This could still happen with the Xantia TD with the Bosch pump, though one doesn't hear of this being such a problem nowadays

[Jogador]

Quick update:
I did the max height then drive test, and for the first few bumps, the car handled like it's supposed to-very smooth.
The further I drowe, the worse was the ride. Did a quick check afterwards, the main pipe to the pump seems to be leaking a bit, so if the lhm can get out, air can get in...it's been a while since I studied physics
I didn't have the tools to tighten the existing clip (factory fitted), I'll just replace it with a more standard one (maybe I'll just replace the lot), tighten firmly and test it again, when I have the time.

I won't start celebrating just yet , but there seems to be light at the end of my (bumpy) tunnel, thank you everybody!

[Mandrake]

A standard screw type jubilee hose clamp is perfect for the job, unless you have the correct tool the original clips are single use...

Which end is leaking, tank or pump ?

[Jogador]

The leak seems to be on the tank-end of the pipe, as the pipe is oily, and a bit loose on the plastic pipe-end.
There was a bit of lhm seeping through on the pump-end when I bought the car, that's when I replaced the clip on that end, and it's been dry ever since.

[Old-Guy]

The front ones are actually a newer type (from a C5- .....

There's your answer - wrong spheres! Wrong because the damping, pressure and maybe volume won't be right. Check these three values in a sphere manufacturer's on-line catalogue.

So you can see my hesitations with buying new spheres, as these show all the examples of perfect health, yet the car rides guite bouncy...

If you order the right spheres, and check the part numbers on the spheres before you fit them (pt no on sphere no = pt no on box is not unknown ) you should have no worries.

[Jogador]

There's your answer - wrong spheres! Wrong because the damping, pressure and maybe volume won't be right. Check these three values in a sphere manufacturer's on-line catalogue.

I'll clarify, the front spheres fit perfectly (confirmed by a specialist who regassed them, so the pressure is also spot on +a bit more, to give a more floaty feel), the only difference is in the outer ring surrounding the membrane. Hydro-geek alert:
A bespoke xantia sphere will allow nitrogen to leak between the membrane and the sphere wall, thus the sphere will loose damping capabilities slowly and can be regassed even when there's almost no pressure left (in reality a few Bar of pressure will be needed to prevent the membrane deforming). The first C5 spheres had a membrane fitted in such a way that there was no possibility of nitrogen escaping through the gap between the sphere wall and the membrane. When these fail, the nitrogen will actually punch a hole through the membrane, thus destroying it.

The same spheres were on the car for the last year or so, and it was gliding like it should, the problem is obviously elsewhere, as the spheres were not even close to flat when I had them regassed (the buffer elements are also in top order, as the spheres have been on the car for a maximum of 15000 miles, and likewise thoroughly checked when they were regassed), and the bouncy ride over short bumps was there before and after treatment.

I got the chance to replace the clips on the pump intake pipe (btw, the lhm in the tank had many bubbles in it when I checked it), and a short test drive later I'm pretty sure, the problem is no more, and am positive it's not as bad as it was before, although I'd need a very bad road to test for sure. Tomorrow I'll bleed the system again, especially the rear brake lines, and lubricate the front struts, and do some extensive citaerobics. This should result in a xantia riding the way it's supposed to

Then I'll also repaint the brake calipers and discs (not on the braking pads ), the refurbished rims really shine, and it would be a shame to ruin the picture with rusty brake calipers.

[Mandrake]

I think you might have a few misconceptions which need clearing up

I'll clarify, the front spheres fit perfectly (confirmed by a specialist who regassed them, so the pressure is also spot on +a bit more, to give a more floaty feel), the only difference is in the outer ring surrounding the membrane.

It's not the only difference - the damper valves are different between Xantia and C5, both the bypass hole diameter and also the threshold valves formed by the washers. You can't tell that the damper valves are tuned differently and by how much just by looking at them visually. For starters the washers on the inside end of the damper valve are not visible at all.

Just because the pressure is correct and the sphere is the same volume doesn't mean it will ride properly if the damper valves are not matched to the car characteristics. If anything the damper valve tuning is more important than the precise gas pressure, which can be +/- 20% without too much problem. (After all the gas pressure drops as the spheres age and its not until they're down to about 50% of the normal pressure that you really start to notice it)

Hydro-geek alert:
A bespoke xantia sphere will allow nitrogen to leak between the membrane and the sphere wall, thus the sphere will loose damping capabilities slowly and can be regassed even when there's almost no pressure left (in reality a few Bar of pressure will be needed to prevent the membrane deforming). The first C5 spheres had a membrane fitted in such a way that there was no possibility of nitrogen escaping through the gap between the sphere wall and the membrane. When these fail, the nitrogen will actually punch a hole through the membrane, thus destroying it.

Wrong on multiple counts... the gas leakage on a conventional single layer Xantia sphere is by diffusion through the membrane itself where the gas meets the oil, as the material (urepan or demopan) is slightly permeable to nitrogen gas, and over many years it diffuses through the membrane into the oil. Because this can only happen when oil is in the bottom of the sphere lifting the diaphragm off the bottom this doesn't happen to a sphere sitting on a shelf as long as the metal button in the middle of the diaphragm seals on the neck of the sphere. Thus shelf life is much greater than working life.

C5 spheres are "multilayer" spheres whose diaphragms consist of three layers instead of one. Two outer standard layers (urepan or desmopan) with a middle non-porous layer whose name escapes me at the moment. The outer flexible layers provide the mechanical strength and help the diaphragm bend in a controlled fashion while the middle non-porous but slightly brittle layer prevents the leakage.

Multilayer Xantia spheres (the ones with the three dimples around the filler cap at the top) are designed much like C5 spheres and can last 10 years without needing regassing. One lesson Citroen learnt with the multilayer design used on some Xantia spheres is that in cold temperatures the middle layer is brittle and has a tendency to crack if the diaphragm is over flexed - in these conditions the center layer splits causing the sphere to lose pressure much faster and mechanically tear the outer layers, so the sphere will fail soon after. Because of this the multilayer spheres were only "trialed" on the front suspension of the Xantia, where the engine bay keeps them warmer than rear spheres. To rectify this C5 spheres were redesigned to be short and squat - thus greatly reducing the required diaphragm flex, making them more robust...

I got the chance to replace the clips on the pump intake pipe (btw, the lhm in the tank had many bubbles in it when I checked it), and a short test drive later I'm pretty sure, the problem is no more, and am positive it's not as bad as it was before, although I'd need a very bad road to test for sure. Tomorrow I'll bleed the system again, especially the rear brake lines, and lubricate the front struts, and do some extensive citaerobics. This should result in a xantia riding the way it's supposed to

If you were seeing quite a bit of frothing in the top of the tank you could have found your problem, there shouldn't be any frothing on the surface of the tank. It's hard to be certain where the air was getting in though, I spent a lot of time trying to hunt down the source of air bubbles in the hydraulic system in my previous Xantia and never completely eliminated it, nor the intermittent harsh/bouncy ride it caused... hopefully you have better luck than me and the joint you fixed was the source of the problem.

[Jogador]

It's not the only difference - the damper valves are different between Xantia and C5, both the bypass hole diameter and also the threshold valves formed by the washers. You can't tell that the damper valves are tuned differently and by how much just by looking at them visually. For starters the washers on the inside end of the damper valve are not visible at all.

If you were seeing quite a bit of frothing in the top of the tank you could have found your problem, there shouldn't be any frothing on the surface of the tank. It's hard to be certain where the air was getting in though, I spent a lot of time trying to hunt down the source of air bubbles in the hydraulic system in my previous Xantia and never completely eliminated it, nor the intermittent harsh/bouncy ride it caused... hopefully you have better luck than me and the joint you fixed was the source of the problem.

It was explained to me differently, but I'm no expert, you do seem to know what you're talking about

The point I was trying to make regarding the C5 spheres is: the same exact ones have been on the car when it was riding smoothly, so it was (to my mind) very unlikely that the drastic deterioration of ride quality was down to the spheres being slightly different than stock.

Onto new business, I fixed the joint, lubricated the front struts (they seem to be in excellent shape though) and bled the brakes (in the crossing order- Front left, rear right, front right, rear left). Especially in the rear brake pipes there was a lot of air, the front ones only had minimal bubbles. Quite normal, as the rear brake lines are very long. Test drive later (along a rough road that was giving me problems before), the car is once more a smooth sailing cruiser, and also under braking much calmer than before.
There may be other souces of air intake, but the ride is back to normal, and for now, my tale of woe has ended

On an unrelated note: I just came back from a blast on the motorway with a DS3 THP156 (the smaller turbo engine)...
The car is a pocket rocket, no other way of describing it, but I wouldn't trade the comfort of my xantia for one, you literally feel every single pebble you drive over

Thanks again for the help, my next post will hoepfully be on a more positive note

[Mandrake]

Glad you got it sorted out and it wasn't too difficult a fix. Keep an eye on it though as I've found if there is only a small amount of air being drawn into the system (or only intermittently) then the ride will be really nice after greasing the front struts, raising the suspension up and down a few times etc, but then after a few days of use the ride will slowly deteriorate again as each time the suspension has to lift a little bit more air will be drawn into the suspension.

[Jogador]

So much for a quck and cheap fix...

The bouncy ride is back

Also, the rear is again starting to shoot up under braking. Once or twice, the rear end even dropped drastically when releasing the brake pedal-this was also the case when I first bought the car and the hydraulics really weren't taken care for (lhm replacement and brake bleeding sorted it right out). There is no frothing in the lhm tank, even when testing with the trick for flushing out air.
My best guess is that the anti-sink membrane is leaking continiously (even more now, since it's been regassed) and the nitrogen is getting into the rear brake circutry (where it can't escape because of the length of rear brake pipes). My only idea, as there's no air bubbles in the lhm tank and this sphere is a reserve for the rear brakes.

Sounds plausible or even possible?

[Xaccers]

Could be the anti sink sphere has now ruptured letting its gas into the rear brake system.
Another bleeding will show if that is the case.

Also while you're under the car, check that the manual height adjuster is situated correctly in the end of the arm that comes out of the actual height corrector.
One of my cars would be really hard at the back, then sometimes it would go soft until I went over a speed bump where it would go hard again.
Turned out the pip on the side of the manual linkage wasn't sitting in the middle of the square hole, it was pressing slightly against one edge of it holding the rear ever so slightly too high.
So the manual and self levelling were fighting each other, the pip would sometimes be pulled out of the square hole and the rear would drop to the right height and be lovely.
Going over a speed bump would send the rear up, the pip would pop back into the hole and prevent the rear dropping down to normal.
The height looked normal though.