Xantia rear suspension

ms00 · Post by **ms00** » 20 Mar 2007, 16:25

Hi Everybody,
Have a problem with a very rigid suspension at the rear of my 96 Xantia 1.8i 16v estate. This has developed over the last couple of weeks.
I have bimbled through the various posts and was just about to order a couple of rear suspension spheres from GSF when I read another post on a different forum which mentioned the anti-sink sphere (in the centre of the rear axle?) having a valve jammed which can cause a similar problem.
I have checked the ride height which is correct. The suspension is now so stiff that the car only travels about 20mm with litl'ol 16st me doing a jig in the boot. This is the same with the engine running or off. After switching the engine off and sitting in the boot the car does not sink and then rise. The front suspension is fine and bounces quite satisfyingly. Selecting various heights with the height selecter works fine although the rear seems slower to react than the front.
So basically do I just need suspension sheres or is there something else I'm missing? The lack of sink and rise when sitting in the boot with the engine off is worrying me.

Post by **CitroJim** » 20 Mar 2007, 16:30

Hi Mick,

Looks like a simple case of completely flat spheres to me given that everything else works normally.

I think if you replace the spheres all will be OK. It would not be a bad idea to replace the anti-sink sphere at the same time just for a job well done as it is likely that if your two suspension sphers are gone, the anti-sink will not be far behind.

Xaccers · Post by **Xaccers** » 20 Mar 2007, 17:03

While you're at it, is the accumulator ticking?
If it needs replacing, might as well do it at the same time while the hydraulic system is depressurised.

Do you know when the car was last hydraflushed?
Shine a torch into the LHM resevoir, the fluid should be green, mine's a rusty brown colour so I'll be flushing mine soon as I get a chance!

FrenchLeave · Post by **FrenchLeave** » 20 Mar 2007, 18:06

The anti sink sphere doesn't - cannot - affect rear suspension softness. The centre hydractive sphere does, assuming of course that you have hydractive on your car.

Post by **Peter.N.** » 20 Mar 2007, 18:39

I concur. The centre hydractive sphere has more affect on the ride than the others!

Post by **CitroJim** » 20 Mar 2007, 19:19

Peter.N. wrote:I concur. The centre hydractive sphere has more affect on the ride than the others!

Indeed, the difference between hard and soft mode is such that you'd think the suspension spheres are flat if the rear is stuck in hard mode. If the hydractive sphere is flat then even if the suspension ECU and electrovalve switches correctly to soft mode it'll still be effectively in hard mode.

Hydractive (if fitted to your car Ms00) is easy to test. Engine stopped at least a minute, put your head a little way under the rear (not too far in!!) and have an assistant open a door. You should hear a click followed by a low buzzing sound as the electrovale opens to put the suspension intio soft mode. Close the door and this low buzzing should end in a distinct click after 30s as the electrovalve closes and the suspension goes back into default hard mode. If you hear a low buzz but no clicks or nothing at all you have a problem with your electrovalves or the wiring to them.

In soft mode, the rear should be just that. Incredibly soft! And in hard, pretty stiff.

If all the above works and there is no difference in feel then the hydractive sphere is flat.

citronut · Post by **citronut** » 20 Mar 2007, 19:22

whilst your crawling around under there give the hight corector manual and self adjusting mechanisum a good dousing with spray on grease

ps.
DO NOT GET UNDER AN UNSUPORTED HYDRAULIC CITROEN
regards malcolm

ms00 · Post by **ms00** » 20 Mar 2007, 21:45

Hi and thanks for your replies,
I apologise one of my posts went awol. The car isn't hydractive. I have no idea when the car was last (or ever!) hydraflushed. However the fluid is the right colour and looks clean-no rust or cloudiness. The front suspension spheres look a lot newer than the rear ones though that might just be due to location.
Sounds like I might just as well replace all rear spheres as Jim suggested. It wont be until next week now due to work commitments. I'll let you know how it goes.
Thanks for your posts,

Richard Stevens · Post by **Richard Stevens** » 12 Jul 2007, 21:01

My 1999 Xantia HDI hydractive has a bouncy rear suspension. On flat roads it’s fine, but give it a couple of bumps in quick succession and the back is like a bronco. This can also happen at high speed, if the road surface is just so – there’s a patch on the M25 near Gatwick that does it.
I have already replaced the hydractive (rear centre) sphere and the rear anti-sink sphere without noticeable change. Whilst in France a mechanic ventured the guess it might be "electronique".
Any suggestions. please?

Mandrake · Post by **Mandrake** » 13 Jul 2007, 00:41

Richard Stevens wrote:My 1999 Xantia HDI hydractive has a bouncy rear suspension. On flat roads it’s fine, but give it a couple of bumps in quick succession and the back is like a bronco. This can also happen at high speed, if the road surface is just so – there’s a patch on the M25 near Gatwick that does it.
I have already replaced the hydractive (rear centre) sphere and the rear anti-sink sphere without noticeable change. Whilst in France a mechanic ventured the guess it might be "electronique".
Any suggestions. please?

The anti-sink sphere wont have any significant effect on the ride.

What about the condition of the rear corner spheres ? They are important too, and provide a lot of the "large bump" absorption and damping. The hydractive centre sphere is more about smoothing the smaller bumps and giving the magic carpet effect.

The rear corner and hydractive spheres both work together in the "soft" mode to contribute to the final result. In the "hard" mode only the corner spheres are operating so if they are flat the ride will be "OKish" in the soft mode, but will become rigid whenever it switches to hard mode. (And bounce on the tyres)

You should be able to establish this with a simple bounce test - let the engine idle and try pressing down the rear - it should be very easy to press down to the bump stops.

Now turn the engine off, leave all doors and boot closed and wait more than 30 seconds - now try sitting on the boot - it should be a lot stiffer than before, but it should still move at least 50mm when you sit on it. If its pretty much rigid then look at replacing those corner spheres...

Regards,
Simon

Richard Stevens · Post by **Richard Stevens** » 15 Jul 2007, 17:28

Simon,
Many thanks for your info. I recognise what you say, and was even out on the car trying the various modes this morning.
In 'soft' mode there's a fair amount of movement, but probably not as much as you suggest there should be. After 30 seconds from closing doors with the engine off it goes virtually solid. The French opinion I got recently kind of steered me away from spheres and I've been attempting to understand the electrics.
By the look of them the rear spheres haven't been replaced (in 8 years) so it's a good move regardless. I attempted to move them a couple of months ago, without success.
Thanks again, I'll let you know the results.

Richard

Richard Stevens · Post by **Richard Stevens** » 29 Jul 2007, 21:33

Sorted! Having read and understood the Technical notes I found on a link, I decided to go ahead and replace the two main rear spheres, as you advised. What a difference! My wife will come driving with me again, so it's a two-edged sword! No really, the notes were great, it's so much better not groping around in the dark, as I was before. I also didn't realise the suspension system is so clever. Many thanks.

Mandrake · Post by **Mandrake** » 30 Jul 2007, 11:55

Hey, great news.

Often people focus too much on the centre sphere and forget the strut spheres, or vica versa - ideally, they should be replaced together as a set of 3 as they all lose pressure at about the same rate, and they all contribute to the ride and handling.

Usually its the centre sphere that gets overlooked because it doesn't exist on a non-Hydractive model, (therefore less familiarity of its existence and purpose) and is well away from the suspension.

Once it goes flat you effectively have the hard mode ride all the time, even when the computer is selecting soft mode.

The other way around - as you had, where the centre sphere is ok but the strut spheres are flat, give a very different scenario - soft mode is stiffer than it should be, but still has some give, but can't cope with large bumps, while the hard mode may be almost rigid - and this can actually be a dangerous handling situation.

Imagine you're taking a fast corner and the rear suspension is in soft mode - then the computer switches you into hard mode to minimize body roll, suddenly the rear suspension goes rigid, because the rear suspension is now suddenly much stiffer than the front it upsets the under/oversteer balance, and the back could potentially oversteer and slide out, particularly on a rough surface.

Something to be aware of.

Also your description of it bouncing at the rear in response to large bumps makes sense - there is a "body movement sensor" at the front that monitors for very large or fast movements of the front suspension, and switches the suspension (both front and rear) into hard mode momentarily to either prevent the suspension bottoming, or control the rebound in response to a violent suspension movement - but with those faulty spheres the rear suspension would become rigid for a moment. Not good...

Regards,
Simon

Richard Stevens · Post by **Richard Stevens** » 30 Jul 2007, 22:02

Simon,
Luckily I had changed the hydractive sphere earlier this year. This was because the suspension felt soft when I got out of the car, so the thinking was that the main spheres were okay. I know different now and it was your assertion that the back should still move down around 50mm (and the system description and diagrams) which convinced me that it had to be the main spheres.
I think we tend to look for the more obscure solutions very often, but ignorance encourages this.
As I said, a Citroen mechanic in France actually leaned on the back of the car, felt the movement, and declared the problem must be electronic. That did throw me off for a while and I determined to find out how the system works.
One thing I haven't found out, though, is the function of the anti-sink sphere. Is it just a pressure head for when the car is parked to prevent sinking, or is there a running function?
Lastly, on the way back home on Saturday with my new spheres (before fitting them) I saw a '98 Xantia estate going along, not very fast, with the front end gently rocking up and down. I wanted to stop and 'do the tests' but there was too much traffic.
Good driving - mine is now!
Regards
Richard

jeremy · Post by **jeremy** » 30 Jul 2007, 22:14

The function of the anti-sink sphere is a bit strange. Basically the system without the anti-sink valve leaks quite nicely which doesn't cause any problems when running but over a short or long while the whole thing depressurises and sinks. (Like BX and older ones and even early Xantias.)

The anti-sink valve is a very tightly machined valve which shuts when the supply pressure drops when the engine is shut off. It locks the pressure in the suspension - but not the rest of the circuit, The anti-sink valve opens when it receives greater pressure from the pump when the engine starts - but the rest of the circuit has no pressure - and so in fact the suspension drops when the valve opens. The sphere provides a reserve of pressure to prevent this.