Xantia Hydractive Cork-Screwing...

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dragen
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Re: Xantia Hydractive Cork-Screwing...

Post by dragen »

Hi (@ Aerodynamica), I assumed it was something hydraulic initially (as is often the case with Citroen), but now that spheres all replaced and EV's are working correctly I'm fairly sure its mechanical, and especially since it is asymmetrical (which I assume would rule out bubbles in the fluid having an impact), and certainly makes the car feel less safe in LH cornering than any other vehicle I have owned - incl. shonky Japanese style vans... :-) Not that it lets go, but there is that over-steer on turn in, not really noticeable below about 60 km/hr, but certainly above. I get used to it on a longer trip, but if I jump out of the pickup/ute or bmw it feels horrific, especially as I live on tight demanding roads with lots of 35/45km/hr corners - and I do throw Frenchie around in those corners... :-D

My tyres are also original overall diameter, and with the correct offset. I am running 215/45 R17, which just take the grip levels pegs above the standard 15" 65 series balloon combination, and even though my end of the road has a few km's of gravel I really don't notice any additional coarseness over the originals. The suspension gives the plush ride, and the tyres allow that Hydractive and everything else to do a bit of magic in those corners. Can really push the car hard, and the suspension soaks it up, but it just keeps gripping...

I'm going to do those swing arm bearings and go from there. Need to grab a couple more tools to make that happen, and I suspect there will be a bit of cursing, but doesn't conceptually look overly complex.

aerodynamica
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Re: Xantia Hydractive Cork-Screwing...

Post by aerodynamica »

Hi, I thought I'd revisit this after a mini update with my car that has (I think) similar issue.

I'd checked virtually everything I could think of: checked and adjusted front wheel alignment, rear arm bearings were done 18 months ago, checked all 4 wheel bearings for play, both front ball joints (one renewed 2 months ago) track rods checked, All spheres are new in the last 6 months, suspension heights correct and both height correctors are rebuilt and modified with sealed bearings in the pivots and work very well, pressure regulator reshimmed and pump reconditioned, new aux belt and LHM and filters cleaned. You'd think it would ride perfectly but it still doesn't!

There's a strange sensation of 'wobbliness' and a definite diagonal 'yaw' at times. I've owned 4 Xantias and this is the only Hydractive one and the only one to do that.

I had a suspicion that there might be some age/ wear- related problem with the Hydractive Firmness Regulators, or perhaps one of the two. I removed the front one and dismantled for inspection of the seat of the electro valve, the valve O ring and the general condition. I've been also getting fast 'tick times' for the pressure regulator and noted that this was massively relieved by disconnecting the Hydractive ECU white plug i.e cutting the system off and reverting to firm Mode permanently. During that mini experiment, the strange sensation over some bumps and curves seemed to go away but it was kind of hard to say because the ride was permanently in firm mode. So I decided to remove the 4 corner spheres and replace them with a set of standard Xantia spheres to effectively have the car run more or less like a standard Xantia. It rides beautifully! And unless I'm hallucinating it has also stopped with the weird, uneven and diagonal feeling it had. It rides like a standard car but with the added benefit of reduced body roll because the firmness regulators prevent cross flow when in firm mode.

Anyway, my theory is that the weird behavior is caused by a fault in the part of the hydractive firmness regulator that stops the LH cross flow.

If you've ever seen the diagrams there's a clever little 'shuttle valve' arrangement that has a ball valve move to one side or the other to block cross flow. The in/out flow of LHM via the height corrector overrides this ball valve by pushing a special internal 'seat' to hold the ball straight. My thinking is that this device has worn and isn't 'shuttling' properly when the car goes through a bend and/ or hits uneven bumps. I think the ball valve either leaks or isn't snapping to one side or the other as quickly as before.

I've been driving the car for a day or so with standard spheres and finding it quite pleasant. I also don't miss the suspension switching to firm mode when you drive away at traffic lights then over some bumps...

With the hydractive permanently 'off' just now the suspension is also staying up a lot longer. It's an early sinking Xantia.

Anyone have any thoughts?

I'm keen to return it to its original functioning Hydractive but really need to find a replacement firmness regulator first (the later type with the modified arrangement)

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white exec
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Re: Xantia Hydractive Cork-Screwing...

Post by white exec »

Hi Graeme,

Are you running with late-type (modified) regulators, or originals? I've lost the plot a bit....sorry.

Your theory about the shuttle ball (anti L-R roll) sounds plausible. Would only take one of those (front or back) to misbehave, and create slewy handling.

Does what you describe sound similar to what you might expect from grossly under-inflated tyres? I known that won't be the case, but just trying to get a feel of the problem.

Good test to run with standard non-HA spheres, and to lock out the HA switching. That narrows down the cause.
C.

Further thought overnight:
Centre (suspension regulator) dampers are there to control sideways roll, before the ball-valve shuts off L-R fluid movement completely.
On Xantia, the centre dampers are different front and back (FF 1.1mm, RR 1.3mm). Wonder if these could accidentally have been swapped around, or mixed up, if the regulators have ever been changed or stripped. (On XM, FF & RR dampers are the same, 1.25mm. Problem if an XM regulator complete were fitted to Xantia.)

Am guessing that you've had the system running on Hydraurincage for a good while. Could only but help if not.

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Re: Xantia Hydractive Cork-Screwing...

Post by aerodynamica »

Hi Chris, you're right but as far as I know all the parts are factory originals.

The later modified type are the ones I'm still holding out for.

This characteristic slowly began showing its effect about a year ago. I'm always fixing and improving bits of the car but I feel that the effect was first noticed shortly after I reshimmed the PRV cut in and cut out thus raising the system pressure. The ride quality improved supporting Simon's theory form years ago about the pressure needing to be high enough to hold the valves open while taking a hammering from the Queen's Highway. I'm not certain why this improvement would cause the wayward sensation though so I'm keeping an open mind about the correlation of fixing the system pressure and the hydractive behaving like that.

aerodynamica
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Re: Xantia Hydractive Cork-Screwing...

Post by aerodynamica »

... also, admittedly i do have non standard wheels, tyres and offset so I may rightly be tricking myself into blaming the hydractive when in fact it's all down to the wheels 🙂

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Re: Xantia Hydractive Cork-Screwing...

Post by aerodynamica »

Apologies on multiple posts.

Just thinking that the overall track is increased at the rear currently and that would certainly give a mechanical advantage in the diagonal direction between say, rear off side spring and front near side if the other factors remained the same. It's intetesting driving the same roads in the hydractive Xantia compared to the '69 ID19. They behave completely different from one another. If anything the D is decidedly less fussy on the rural twisty A roads - it floats on seemingly endless wheel travel but occasionally suffers a kind of snap oversteer on a particular sweeping uphill bend as though the rear kind of jumps up and tops out, something none of my 4 CXs, 2 XMs, GSA, 2 BXs and 4 Xantias did. I don't thin n the ID19B 's power output really encourages that kind of driving though 🤣 the manual XM SEi Turbo did though.

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white exec
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Re: Xantia Hydractive Cork-Screwing...

Post by white exec »

If you still have the standard wheels, I suppose you could try them...

aerodynamica
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Re: Xantia Hydractive Cork-Screwing...

Post by aerodynamica »

That's the trouble Chris, I sold them! I'm now regretting that as I could've used this time to refurb them. They're quite hard to come by too.
I just tested the 4 corner spheres that have the manufacture date of one year ago. The fronts: hydractive XM 55 FH, are actually XM fronts, they're the only 55 bar front hydractive i could find. They tested at 50 bar each. The rears are XA 30 RH and are the right ones for this Xantia. They tested at 27 bar each.
So that's about right for a year's loss. It's reassuring to find that they're losing pressure at an equal rate.

Also, when I said the substitute corner spheres were standard Xantia, I was glossing over. They're close to standard but in fact the rears I fitted are actually the former fronts that were 50 bar but had gone down to 40 (about right for the rear) I enlarged the central hole from the almost invisibly small size to first: 0.7mm but that proved too stiff so second: 1.1mm with a dremel. And that is a lot better. It's still slightly stiffer than standard due tho the extra damper disks but not too bad. The front pair are a modified set from my ID19. They're 500cc that had a pressure measured at 50 bar (should be 75) the damper is way too soft though so i drilled the center rivet to 5mm to s depth of 6mm and then used a plug tao to tap to M6 x 1.0. This gave a fitting to allow a modified s/steel screw to be drilled through on a lathe to 1.0mm. Wfen fitted in the M6 bore it replaces the original damper hole with a far smaller one. It worked week and I've driven the car these last days with this set up.

Mind you to say it's running standard would be untrue! The front, even with the mod, is actually still a bit too soft so today I performed a similar mod to a pair of regassed 400cc former BX fronts now with a smaller damper hole.

Oddly I'm tempted to return it to hydractive already because it doesn't seem right without the hydractive quirks! I keep expecting to hear the familiar harmonic sound of the 2 electrovalves after parking up..

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Re: Xantia Hydractive Cork-Screwing...

Post by aerodynamica »

Sorry about the typos - it's the phone autocorrect - I don't always spot them.

The modified BX fronts are 50 bar measured today. It's intetesting to note that these were spheres that were recharged to about 60 bar back in 2008. It's incredible they've only lost 10 bar in 11 years and certainly goes to show that recharged spheres do last if it's done correctly.

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white exec
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Re: Xantia Hydractive Cork-Screwing...

Post by white exec »

Thanks for all the extra detail, Graeme.
The set-up is so non-standard now that I wouldn't be confident trying to predict exactly how it would now operate.
As we know, the sphere dampers function with two separate, and preset, mechanisms: the central hole and the two sprung washer stacks. These will have been carefully chosen to produce the required ride characteristics, and been tweaked during development by practical testing. On paper, the differences between models looks tiny, but obviously results in quite different behaviour.
I think the only way to rescue the situation (if desired) is to return to completely standard spec (HA or not) with known good new spheres, and go from there. At least you have access to sphere testing/regassing, which will save a good few bob.
All good fun, though! :wink:

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Re: Xantia Hydractive Cork-Screwing...

Post by aerodynamica »

True, and having now driven 25 miles with the modified old BX fronts, I think the spec is still wrong. The damping characteristic isn't right despite the center hole being in spec, the disk stack must be set up for BX struts and the axle weight and not quite right for the Xantia. It's good and very smoth but on occasion on the motorway it feels like it reacts badly to sudden dips. I think I'll refit the hydractive spheres after all and plug the Hydractive ECU back in. I'll just have to live with the fast regulator click time for now until I source a replacement front firmness regulator. I had found a NOS item on ebay but it is the original type, not the modified type.

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Re: Xantia Hydractive Cork-Screwing...

Post by xantia_v6 »

Fast regulator tick while in soft mode is in my experience always caused by the electrovalve, not the main hydractive valve block, so may be you have two problems. The main valve block does not have a LHM return pipe, so cannot have an internal leakage back to the LHM tank.

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Re: Xantia Hydractive Cork-Screwing...

Post by aerodynamica »

That's a good point - It didn't occur to me that all the hydraulics in the Hydractive block were 'fed' as they're all down stream from the height corrector and/or security valve.

I did suffer a blown rubber return pipe from the front electrovalve about a year ago but I just put that down to aged rubber.

Do you know what the particular leakage point on the electro valve is? I fitted a new O ring to it a few months ago because the original one was all cracked and I thought it might be the cause but I was mistaken.

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Re: Xantia Hydractive Cork-Screwing...

Post by aerodynamica »

Mini update: I refitted the 4 corner spheres and after priming and citaerobics and letting it sit idle for half and hor to allow the bubbles returned to the tank to top out, I reconnected the ECU and topped up the LHM. Took it for a spin and find that the ride is better than ever, hydractive switching is seemless (it's often seen to be quite 'stepped' between stiff and soft springing) also the tick times are improved. Why would this be? I've done nothing but essentially give the 2 electrovalves a rest for 4 days. I imagine the fast tick times will return.

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Re: Xantia Hydractive Cork-Screwing...

Post by xantia_v6 »

See this topic for some ideas... viewtopic.php?t=31881