Xantia Hydractive Cork-Screwing...

[dragen]

Howdy folks. I have a 98 TD Xantia Hydractive which has developed an odd (hard to think of an appropriate term or analogy) corkscrewing motion when taking left-hand sweeping corners at speed. On turn in it loads up on the RHS of car as the weight transfers to that side, then it suddenly tightens and does an over-steer inducing roll which pulls the nose towards the corner apex, then that releases towards an understeer, then tightens again to make a sinusoidal path through the corner. Its disconcerting, but behaving somewhat normally on right-hand corners.

Have removed/checked regassed/replaced spheres as necessary this week (have just put in a pair of overly soft BX spheres on the back today) but otherwise are all good, and this motion had begun before having this sphere issue develop a fortnight ago. My suspicion on the drive home tonight was that it could be in relation to an anti-roll bar, and will be getting it up on blocks tomorrow for a futher inspection, but would super appreciate any other tips on things to look at.

Cheers team Citroen!

[white exec]

I know you said that the problem pre-dates the soft BX-spec spheres at the rear, but the use of those on the rear corners could seriously impair stability, because, when seriously cornering, the car will switch to Firm mode (which is provided by the relatively stiff corner spheres, working on their own), only to find that that stiffness just will not be there - just a bucket of softness! That could cause the front (stiff) corners not to remain properly in contact with the road, and give lack of front-end control. If you are going to go for non-standard super-Softness, you must do it all round. The Xantia is built around relatively small amounts of suspension movement (compared to CX, BX, etc) and so very soft spheres (either large volume, or low levels of damping) might well not be what it was designed to cope with.

But, as you said, it pre-dates that mod... So check roll-bars, front-end rubber bushing, tyre-pressures, steering joints. Others here will be able to pitch in with more suggestions.

[dragen]

Hi Chris, yes cheers for those cautions, well noted. My understanding is the hydractive has quite stiff corner sphere's while the centres provide that softness in 'normal' mode, if thats correct? Those BX sphere's were just what had on-hand, but it is the exact same motion that was occurring before the swap out. It has provided a plusher tail thats for sure, but certainly not what I want other than temporarily while I source replacements and isolate what this problem is. Cheers for the points, tyres are all good, and it is on 215/45 R17 tyres at 32F/28R psi.

[Stickyfinger]

My Mk1 C5 (same design basically) had a "inside Rear tucking under" problem....it turned out to be the rear arm bearing on the near side.
It made for some VERY amusing "moments".

[GiveMeABreak]

I agree with Chris - you are basically negating the 'firm' mode of the system. It's the same with my XMs - once 'comfort' spheres were put on to get the soft ride we were used to from the CX days, it basically wiped out any effect of the sport mode setting. So wallowed and pitched a lot more. I ended up going back to standard spheres because the windy Welsh roads where I am made it impossible - without copious amounts of super glue on the seats.

Worn drop links will also cause the sudden 'cutting in' at the fronts when cornering as if the car is slipping.

[dragen]

I have no desire to keep those bx sphere's on, just an emergency temporary when the rear's went hard and were nearly throwing me off the road, let alone on the gravel and crossing paddocks... With the tight winding roads I'm on I prefer handling to super plushness. Tbh I have never noted a huge difference between normal and sport modes on the xantia...

[admiral51]

Is it possible you a have wire that is not secure and has been rubbing through the outer cable and now is giving false readings to the suspension ECU under certain situations?
Just guessing but it seems to me that it is switching between sport/normal modes and you say it seems okay in left hand but not right hand curves?

[white exec]

Tbh I have never noted a huge difference between normal and sport modes on the xantia...

On (non-Activa) Xantia - which has Hydractive II suspension - the soft ride (and the firm one) will be the same degree of softness (or firmness) whether you are in Normal or Sport modes.

What changes when you opt for Sport is that the thresholds when the system switches to Firm are changed. In Sport mode, the flip to Firm will happen much more readily as the various sensors (steering, accelerator, body movement...) sense how the car is being driven briskly. In Sport mode, the car will spend more time in Firm, unless you relax your driving, when it will revert to Soft.

On the older version of Hydractive (now called Hydractive I) in the early '90s, the Sport button immediately firmed up the ride (above about 18mph) and kept it there. With H.II, this doesn't happen: even in Sport mode, you can drive away from rest and tootle about gently with the suspension remaining Soft.

Now, if there is no detectable difference on your car between the two modes, or if Soft and Firm both feel the same - or if Soft seems missing - then there is a fault.

To check whether both modes are available, do a "bounce test":
- Engine running, car at Normal height
- Press down heavily on the rear end, and body should go down fairly easily by 15cm or so; this should be Soft mode
- Front of car will also be Soft, but will go down a bit less easily, and by about half the amount.
- Switch engine off, and close all the doors
- After 30 secs, you should hear the front and rear Electrovalves click off, together. This will put the car into Firm mode.
- Push down at rear again, and the car should feel much more solid, and difficult to depress. Same at the front.
- Re-opening a door should immediately bring back Soft mode, until the door is closed again, and the 30sec of Soft will commence and terminate again.

That test shows that both modes are available, and the Electrovalves, hydraulics and spheres are operating as they should.

Let us know what you find.

[dragen]

Awesome, much appreciated feedback. I'll have it up on a hoist a bit later today for a good look around, shall let you all know what I find.

[xantia_v6]

It would be worth re-checking your front spheres, I had similar symptoms when a corner sphere failed a few days after fitting. It was a NOS genuine sphere, but the diaphragm did not like the unaccustomed flexing.

[dragen]

Got it on the hoist and had a good poke around, nothing obvious interms of links with the front anti-roll bar, any worn bushes, play that I could detect anywhere, etc.
@xantia_v6: As you say it might be time to return to those front spheres...
@white exec: Cheers for that, yes went through that bounce test routine and seemed all good.

[white exec]

If one of the front/corner spheres has lost its gas/failed, the bounce test will still show that Soft is present, because Soft is provided by the centre (hydractive) sphere being in circuit. When it is switched out (EVs go off), only the corner spheres remain, and if any of those are "flat", then the ride/bounce will still show Firm . . . but very firm, and bouncy/unpleasant on anything other than a dead-smooth road when operating in Firm.

Check or substitute the suspect spheres.

[dragen]

Seems to be 'clunking' more from that suspect front-right on bad surfaces too, definetly going to check that again when get the chance. I've been hunting around online and looking at sphere tables, etc. for new/replacement spheres (bit over the hodge podge that have here and would like to get back to fresh and original spec). Can get the 4 corners plus the two hydractive for NZD250 in the UK (great value Monroe numbers), but then add $290 in shipping on top of that, ouch! Any other recommended sources, or in particular Australasia/NZ? Cheers

[white exec]

250NZD (€150) is v.cheap for 6 spheres.
I recall some negative comments about Monroe (as well as Lizarte) spheres, but that was a while ago. Others may have recent more experience.

If you get stuck with a high sphere price, and intend keeping the car for a good while, it might be worth considering acquiring the Tecnosir re-gassing tool C720 (was about €100, direct from T.) and a locally-sourced cylinder of nitrogen.
http://www.tecnosir.com/attrezzature_c720.php?lang=en

The kit also allows checking of sphere pressure, once the spheres have been fitted with the Valprex valves.
Re-gassing/topping-up usually advisable every 2-3 years.
Allows decent spheres to have a longer life, as it avoids damage due to low pressure.
Also enables a check/top-up on 'new' spheres, which may have been in storage for some time.

Have had the kit here for several years now, and it allows being self-sufficient when it comes to sphere maintenance, and takes a chunk of guesswork out of suspension performance.

[dragen]

Hi Chris, yes defininetly thinking about getting one of the technosir, looks real handy and easy re-gas/check setup, great feeback on that quality aspect too. I might have a look at french/german sources again, see what find in terms of brands and pricing - apparently shipping often way cheaper than from the UK. Cheers